Additions and notes by James Renwick, LL.D.

Philadelphia: Carey and Hart, 1836.

Ed. Downloaded from the U. of Rochester Steam Collection (http://www.history.rochester.edu/steam/), some corrections and additions made based on the original text. This excerpt contains Chapters 13 & 14.  JMcV., May 2008


Steam Navigation.


Among the many ways in which the steam-engine has ministered to the advancement of civilisation and social progress of the human race, there is none more important or more interesting than its application to navigation. Before it lent its giant powers to the propulsion of steam locomotion over the waters of the deep was attended with so much danger and uncertainty that, as a common proverb, it became the type and the representative of every thing which was precarious and perilous. The application, however, of steam to navigation has rescued the mariner and the voyager from many of the dangers of wind and water; and even in its present state, putting out of view its probable improvement, it has rendered all voyages of moderate length as safe, and very nearly as regular, as journeys overland. As a means of transport by sea, the application of this power may be considered as established; and it is now receiving improvements by which its extension to the longest class of ocean voyages is a question not of practicability, but merely of profit.

The manner in which the steam-engine is rendered an instrument for the propulsion of vessels must in its general features be so familiar to every one as to require but short explanation. A shaft is carried across the vessel, being continued on either side beyond the timbers: to the extremities of this shaft, on the outside of the vessel, are fixed a pair of wheels constructed like undershot waterwheels, having attached to their rims a number of flat boards called paddle-boards. As the wheels revolve, these paddle-boards strike the water, driving it in a direction contrary to that in which it is intended the vessel should be propelled. The moving force imparted to the water thus driven backwards is necessarily accompanied by a reaction upon the vessel through the medium of the paddle-shaft, by which the vessel is propelled forwards. On the paddle-shaft two cranks are constructed, similar to the cranks already described on the axle of the driving wheels of a locomotive engine. 'These cranks are placed at right angles to each other, so that when either is in its highest or lowest position the other shall be horizontal. They are driven by two steam-engines, Which are placed in the hull of the vessel below the paddle-shaft. In the earlier steamboats a single steam-engine was used, and in that case the unequal action of the engine on the crank was equalised by a flywheel. This, however, has been long  since abandoned In European vessels, and the use of two engines is now almost universal. By the relative position of the cranks it will be seen, that when either crank is at its dead points, the other will be in the positions most favourable to its action, and in all intermediate positions the relative efficiency of the cranks will be such as to render their combined action very nearly uniform. The steam-engines used to impel vessels may be either condensing engines, similar to those of Watt, and such as are used in manufactures generally, or they may be non condensing and high-pressure engines, similar in principle to those used on railways. Low-pressure condensing engines are, however, universally used for marine purposes in Europe and to some extent in the United States. In the latter country, however, high-pressure engines are also in pretty general use, on rivers where lightness is a matter of importance The arrangement of the parts of a marine engine differs in some respects from that of a land engine. The limitation of space, which is unavoidable in a vessel, renders greater compactness necessary. The paddle-shaft on which the cranks to be driven by the engine are constructed being very little below the deck of the vessel, the beam and connecting rod could not be placed in the position in which they usually are in land engines, without carrying the machinery to a considerable elevation above the deck. This is done in the steamboat engines used on the American rivers; but it would be inadmissible in steamboats in general, and more especially in seagoing steamers. The connecting rods, therefore, instead of being presented downwards towards the cranks which they drive, must, in steam-vessels, be presented upwards, in the impelling force received from below. If, under these circumstances, the beam were in the usual position above the cylinder and piston-rod, it. must necessarily be placed between the engine and the paddle-shaft. This would require a depth for the machinery which would be incompatible with the magnitude of the vessel. The beam, therefore, of marine engines, instead of being above the cylinder and piston, is placed below them. To the top of the  piston-rods cross pieces are attached of greater length than the diameter of the cylinders, so that their extremities shall project beyond the cylinders. To the ends of these cross pieces are attached by joints the rods of a parallel motion : these rods are carried downwards, and are connected with the ends of two beams below the cylinder, and placed on either side of it. The opposite ends of these beams are connected by another cross piece, to which is attached a connecting rod, which is continued upwards to the crank-pin, to which it is attached, and which it drives. Thus the beams parallel motion, and connecting rod of a marine engine, is similar to that of a land engine, only that it is turned upside down; and in consequence of the impossibility of placing the beam directly over the piston-rod, two beams and two systems of parallel motion are provided, one on each side of the engine, acted upon by, and acting on the piston-rod and crank by cross pieces. The proportion of the cylinders differs from that usually observed in land engines, for like reasons. The length of the cylinder of land engines is generally greater than its diameter, in the proportion of about two to one. The cylinders of marine engines are, however, commonly constructed with a diameter very little less than their length. In proportion, therefore, to their power their stroke is shorter, which infers a corresponding shortness of crank and a greater limitation of play of all the moving parts in the vertical direction. The valves and the gearing by which they are worked, the air-pump, the condenser, and other parts of the marine engines, do not materially differ from those already described in land engines. These arrangements of a marine engine will be more clearly understood by reference to fig. 119. in which is represented a longitudinal section of a marine engine with its boiler as placed in a steam-vessel. The sleepers of oak, supporting the engine, are represented at x, the base of the engine being secured to these by bolts passing through them

Fig. 119

and the bottom timbers of the vessel; s is the steam-pipe leading from the steam-chest in the boiler to the slides c, by which it Is admitted to the top and bottom of the cycle The condenser is represented at B, and the air-pump at E. The hot well is seen at F, from which the feed is taken for the boiler; L is the piston-rod connected by the parallel motion a with the beam H, working on a centre K, near the L base of the engine. The other end of the beam I drives the connecting rod m, which extends upwards to the crank it works upon the paddle-shaft Q. R is the framing by which the engine is supported. The beam here exhibited is shown on dotted lines as being on the further side of the engine. A similar beam similarly placed, and moving on the same axis, must be understood to be at this side connected with the cross head of the piston in a like manner by a prior motion, and with a cross piece attached to the lower end of the connecting rod and to the opposite hewn. The eccentric which works the slides is placed upon the paddle L and the connecting arm which drives the slides may be easily detached when the engine requires to be stopped. Sections of the boiler, grate, and flues is represented at w-u. The safety-valve y is enclosed beneath a pipe carried beside the chimney and is inaccessible to the engine. They are the cocks responsible for blowing the salted water from the boiler and I-I the feed-pipe. The general arrangement of the engine-room of a steam vessel is represented in fig 120. The nature of the effect required to be produced by steam engines does not render either necessary or possible. One great regularity of action which is indispensable in a steam engine is applied to the pipes of manufacture. The eccentric of the surface of the sea wall causes the immersion of the paddle-wheels to be subject to great variation, and the resistance produced by the water to the engine will undergo a corresponding change. The governor, therefore, and other parts of the apparatus, contrived for giving to the engine that great regularity required in manufactures, are omitted in nautical engines, and nothing is introduced save what is necessary to maintain the machine in its full working efficiency.

Fig. 120

To save space, marine boilers are constructed so as to produce the necessary quantity of steam within the smallest possible dimensions.

Fig. 121

With this view a more extensive surface in proportion to the capacity of the boiler is exposed to the action of the fire. The flues, by which the flame and heated air are conducted to the chimney, are so constructed that the heat may act upon the water on every side in thin oblong shells or plates. This is accomplished by constructing the flues so as to traverse the boiler backwards and forwards several times before they terminate  in the chimney. Such an arrangement renders the expense of the boilers greater, but their steam producing power is proportionally augmented, and experiments made by Mr. Watt, at Birmingham, have proved that such boilers with the same consumption of fuel will produce, as compared with common land boilers, an increased evaporation in the proportion of about three to two. M

The form and arrangement of the water-spaces and flues in marine boilers may be collected from the sections of the boilers used in some of the government steamers, exhibited fig. 121, 122, 123. A section made by a horizontal plane passing through the flues is exhibited in fig. 121. The furnaces F communicates in pairs with the flues E the air following the course through the flues represented by the arrows. The flue E passes to the back of the boiler, then returns to the front, then to the back again, and is finally carried back to the front, where it communicates at c with the curved flues represented in the transverse vertical section, 122. This curved flue B finally terminates in the chimney A. There are in this case three independent boilers, each worked by two furnaces communicating with the same system of flues; and in the curved flues B fig. 1 22., by which the air is finally conducted through the chimney, are placed three independent dampers, by means of which the furnace of each boiler can be regulated independently of the other, and by which each boiler may be separately detached from communication with the chimney The letters of reference in the horizontal section, fig. 121, correspond with those in the transverse vertical section, fig 122., with E representing the commencement of the flues, and C their termination. A longitudinal section of the boiler made by a vertical plane extending from the front to the back is given in fig 123,  where f, as before, is the furnace, g the grate-bars sloping downwards from the front to the back, h the fire-bridge, c the commencement of the flues, and A the chimney. An elevation of the front of the boiler is represented in fig. 124., showing two of the fire-doors closed, and the other two removed, displaying the position of the grate-bars in front. Small openings are also provided, closed by proper doors, by which access can be had to the under side of the flues between the foundation timbers of the engine for the purpose of cleaning them. Each of these boilers can be worked independently of the others. By these means, when at sea, the engine may be worked by any two of the three boilers, while the third is being cleaned and put in order. In all seagoing steamers, multiple boilers are present providing for this purpose.. In the boilers are represented the flues all upon the same level, winding backwards and forwards without passing one above the other. In the other boilers, however, the flues, after passing backwards and forwards near the bottom of the boiler, turn upwards and pass backwards and forwards through a level of the water nearer its surface, finally terminating in the chimney. More heating surface is thus obtained with the same capacity of boiler. The most formidable difficulty which has been encountered in the application of the steam-engine to sea voyages, has arisen from the necessity of supplying the boiler with sea water instead of pure fresh water. The sea-water is injected into the condenser for the purpose of condensing the steam, and it is thence, mixed with the condensed steam, to be conducted as feeding water into the boiler.


Fig 123                                                                Fig. 124


 Sea-water holds, as is well known, certain alkaline substances in solution, the principal of which is muriate of soda, or common salt. Ten thousand grains of pure ;sea water contain two hundred and twenty grains of common salt, remaining ingredients being thirty-three grains of sulphate of soda, forty-two grains of muriate of magnesia, and eight grains of muriate of lime. The heat which converts pure water into steam does not at the same time evaporate those salts which the water holds in solution. As a consequence, it follows, that as evaporation in the boiler is continued, the salt, which was held in solution by the water which been evaporated, remains in the boiler, and enters into solution with the water remaining in it. The quantity of salt contained in sea-water being considerably less than that which water is capable of holding in solution, the process of evaporation for some time is attended with no other effect than to render the water in the boiler a stronger solution of salt. If, however, this process be continued, the quantity of salt retained in the boiler having constantly an increasing proportion to the quantity of Water, it must at length render the water in the boiler a saturated solution-that is, a solution containing as much salt as at the actual temperature it is capable of holding in solution. If, therefore, the evaporation be continued beyond this point, the salt disengaged from the water evaporated instead of entering into solution with the water remaining in the boiler will be precipitated in the form of sediment; and if the process be continued in the same manner, the boiler would at length become a mere salt-pan. But besides the deposition of salt sediment in a loose form, some of the constituents of sea-water having an attraction for the iron of the boiler, correct upon it in a scale or crust in the same manner as earthy matters held in solution by spring-water are observed to form and become incrusted on the inner surface of land-boilers and of common culinary vessels. The coating of the inner surface of a boiler by incrustation and the collection of salt sediment in its lower parts, are attended with effects highly injurious to the materials of the boiler. The crust and segment thus formed within the boiler are almost nonconductors of heat, and placed, as they are, between the water contained in the boiler and the metallic plates which form it, they obstruct the passage of heat from the outer surface of the plates in contact with the fire to the water. The heat, therefore, accumulating iii the boilerplates so as to give them a much higher temperature than the water within the boiler, has the effect of softening them, and by the unequal temperature which will thus he imparted to the lower plates which are incrusted, compared with the higher parts which may not he so, an unequal expansion is produced, by which the joints and seams of the boiler are loosened and opened, and leaks produced. These injurious effects can only he prevented by either of two methods; first, by so regulating the feed of the boiler that the water it contains shall not be suffered 'to reach the point of saturation, but shall be so limited in its degree of saltness that no injurious incrustation or deposit shall be formed; secondly, by the adoption of some method by which the boiler may be worked with fresh water.' This end can only be attained by condensing the steam by a jet of fresh water, and working the boiler continually by the fresh water, since a supply of fresh water sufficient for a boiler worked in the ordinary way could never be commanded at sea.

The method by which the saltiness, of the water in the boiler is most commonly prevented from exceeding a certain limit has been to discharge from the boiler into the sea a certain quantity of over-salted water, and to supply its place introduced into the condenser through the injection-cock for the purpose of condensing the steam, this water being mixed with the steam so condensed, and being, weaker solution of salt than common sea-water. therefore, a To effect this, cocks called blow-off cocks, are usually placed in the lower parts of the boiler, where the over-salted, and therefore heavier, parts of the water collect. The pressure of the steam and incumbent weight of the water in the boiler force the lower strata of water out through these cocks; and this process, called blowing out, is, or ought to be, practised at such intervals as will prevent the water from becoming has been blown out in over salted. When the salted water has been blown out in this manner, the level of the water in the boiler is restored by a feed of corresponding quantity. This process of blowing out, on the due and regular observance of which the preservation and efficiency of the boiler mainly depend, is too often left at the discretion of the engineer, who is, in most cases, not even supplied with the proper means of ascertaining the extent to which the process should be carried. It is commonly required that the engineer should blow out a certain portion of the water in the boiler every two hours, restoring the level by a feed of equivalent amount; but it is evident that the sufficiency of the process founded on such a rule must mainly depend on the supposition that the evaporation proceeds always at the same rate, which is far from being the case with marine boilers. An indicator, by which the saltness of the water in the boiler would always be exhibited, ought to be provided, and the process of blowing out should be regulated by the inclinations of that instrument. To blow out more frequently than is necessary is attended with a waste of fuel ; for hot water is thus discharged into the sea while cold water is introduced in its place, and consequently all the heat necessary to produce the difference of the temperatures of the water blown out and the feed introduced is lost. If, on the other hand, the process of blowing out be observed less frequently than is necessary, then more or less incrustation and deposit may be produced, and the injurious effects already described ensue As the specific gravity of water holding salt in solution is increased with every increase of the strength of the solution, any form of hydrometer capable of exhibiting a visible indication of the specific gravity of the water contained in the boiler would serve the purpose of an indicator, to show the process of blowing out is necessary, and when it has been carried to a sufficient extent. The application of such instruments, however, would be attended with some practical difficulties in the case of sea-boilers. The temperature at which a solution of salt boils under a given pressure varies considerably with the strength of the solution ; the more concentrated the solution is, the higher will be its boiling temperature under the same pressure. A comparison, therefore, of a steam-gauge attached to the boiler, and a thermometer immersed in it, showing the pressure and the temperature, would always indicate the saltness of the water; and it would not be difficult so to graduate these instruments as to make them at once show the degree of saltness.

If the application of the thermometer he considered to be attended with practical difficulty, the difference of pressures under which the salt water of the boiler and fresh water of the same temperature boil, might be taken as an indication of the saltness of the water in the boiler, and it would not be difficult to construct upon this principle a self-registering instrument, which would not only indicate but record from hour to hour the degree of saltness of the water. A small vessel of distilled water being immersed in the water of the boiler would always have the temperature of that water, and the steam produced from it communicating with a steam-gauge, the pressure of such steam would be indicated by that gauge, while the pressure of the steam in the boiler under which pressure the salted water boils might be indicated by another gauge. The difference of the pressures indicated by the two gauges would thus become a test by which the saltness of the water in the boiler would be measured. The two pressures might be made to act on opposite ends of the same column of mercury contained in a siphon tube, and the difference of the levels of the two surfaces of the mercury would thus become a measure of the saltness of the water in the boiler. A self registering instrument founded on this principle formed part of the self-registering team-log which I proposed to introduce into steam-vessels some time since. (21 1.) The Messrs. Seaward of Limehouse have adopted, in some of their recently constructed engines, a method of indicating the saltness of the water, and of measuring the quantity of salted water or brine discharged, by blowing out. A glass gauge, similar in form to that already described in land engines (156.), is provided to indicate the position of the surface of the water in the boiler. In this gauge two hydrometer balls are provided, the weight of which in proportion to their magnitude is such that they would both sink to the bottom in a solution of salt of the same strength as common sea-water. When the quantity of salt exceeds 5/52 parts of the whole weight of the water, the lighter of the two balls Will float to the top; and when the strength is further increased until the proportion of salt exceeds, 6/52 parts of the whole, then the heavier ball will float to the top. The actual quantity of salt held in solution by sea-water in its ordinary state is ', part of its whole weight; and when by evaporation the proportion of salt in solution has become 9/52 parts of the whole, then a deposition of salt commences. With an indicator such as that above described, the ascent of the lighter hydrometer ball gives notice of the necessity for blowing out, and the ascent of the heavier may be considered as indicating the approach of an injurious state of saltness in the boiler. The ordinary method of blowing out the salted water from a boiler is by a pipe having a cock in 'it leading from the boiler through the bottom of the ship, or at a point low down at its side. Whenever the engineer considers that the water in the boiler has become so salted that the process of blowing out should commence, he opens the cock communicating by this pipe with the sea, and suffers an indefinite and uncertain quantity of water to escape. In this way he discharges, according to the magnitude of the boiler, from two to six tons of water, and repeats this at intervals of from two to four hours, as he may consider to be sufficient. If, by observing this process, he prevents the boiler from getting incrusted during the voyage, he considers his duty to be effectually discharged, forgetting that he may have blown out many times more water than is necessary for the preservation of the boiler, and thereby produced a corresponding and unnecessary waste of fuel. In order to limit the quantity of water discharged, Messrs. Seaward have adopted the following method. In fig. 125. is represented a transverse section of a part of a steam-vessel; w is the waterline of the boiler, B is the mouth of a blow-off pipe, placed near the bottom of the boiler. This pipe rises to A, and turning in the horizontal direction, A c is conducted to a tank T, which contains exactly a ton of water. This pipe communicates with the tank by a cock D, governed by a lever it. When this lever is moved to DI, the cock D is Open, and when it in moved to K, the cock D is closed. From the same tank there proceeds another pipe F, which issues from the side of the vessel into the sea governed by a cock v, which is likewise put in connection with the lever H, so that it shall be opened when the lever H is drawn to the Position F', the cock D` being closed in all positions of the lever between x and V. Thus, whenever the cock F communicating with the sea is open, the cock D` communicating with the boiler is closed, and vice versa, 'both cocks being closed when the lever is in the intermediate position K. By this arrangement the boiler cannot, by any neglect in blowing off, be left in communication with the sea, nor can more than a ton of water be discharged except by the immediate act of the engineer. The injurious consequences are thus prevented which sometimes ensue when the blow-off cocks are left open by any neglect on the part of the engineer. When it is necessary to blow off, the engineer moves the lever H, to the position D". The pressure of the steam in the boiler on the surface of the water w forces the salted water or brine up the pipe B A, and through the open cock c into the tank, and this continues until the tank is filled: when that takes place, the lever is moved from the position D' to tile position P', by which the cock D is closed, and the cock F opened. The water in the tank flows through the pipe E into the sea, air being admitted through the valve Y, placed at the top of the tank, opening inwards. A second ton of brine is discharged by moving the lever back to the position V, and subsequently returning it to the position F; and in this way the brine is discharged ton by ton, until the supply of water from the feed which replaces it has caused both the balls in tile indicator to sink to the bottom (212)

Fig. 125

A different method of preserving the requisite freshness of the water in the boiler has been adopted by Messrs. Maudslay and Field, and introduced with success into the Great Western and other steam-vessels. Pumps called brine-pumps are put into communication with the lower part of the boiler, and so constructed as to draw the brine therefrom, and drive it into the sea. These brine-pumps are worked by the engine, and their operation is constant. The feed-pumps are likewise worked by the engine, and they bear such a proportion to the brine-pumps that tile quantity of salt discharged in a given time in the brine is equal to the quantity of salt introduced in solution by the water of the feed-pumps. By this means the same actual quantity of salt is constantly maintained in the boiler, and consequently the strength of the solution remains invariable. If the brine discharged by the brine-pumps contains 5/32 parts of salt while the water introduced by the feed-pumps contains only 1/32 part, then it is evident that five cubic feet of the feeding water will contain no more salt than is contained in one cubic foot of brine. Under such circumstances the brine-pumps would be so constructed as to discharge 1/5 of the water introduced by the feed-pumps, so that 4/5 of all the water introduced into the boiler would be evaporated, and rendered available for working the engine. To save the heat of the brine, a method has been adopted in the marine engines constructed by Messrs. Maudslay and Field similar to one which has been long practised in steam boilers, and in various apparatus for the warming of buildings. The current of heated brine is conducted from the boiler through a tube which is contained in another, through which the feed is introduced. The warm current of brine, therefore, as it passes out, imparts a considerable portion of its heat to the cold feed which comes in ; and it is found that by this expedient the brine discharged into the sea may be reduced to a temperature of about 100'. This expedient is so effectual that when the apparatus is properly constructed, and kept in a state of efficiency, it may be regarded as nearly a perfect preventive against the incrustation, and the deposition of salt in the boilers, and is not attended with any considerable waste of fuel. (213) About the year 1776, Mr. Watt invented a tubular condenser, with a view to condense the steam drawn off from the cylinder without the process of injection. This apparatus consisted of a number of small tubes connecting the top and bottom of the condenser, arranged in a manner not very different from that of the tubes which traverse the boiler of a locomotive engine. These tubes were continually surrounded by cold water, and the steam, as it escaped from the cylinder passing through them, was condensed by their cold surfaces, and collected in the form of water in a reservoir below, from whence it was drawn off by a pump in the same manner in engines which condensed by injection. One of the advantages proposed by this expedient was, that no atmospheric air would be introduced into the condenser, as is always the case when condensation by injection is practised. Cold Water which is injected, has always combined with it more or I common air. When this water is mixed with the condensed steam, the elevation of its temperature disengages the air combined with it, and this air circulating to the cylinder vitiates the vacuum. One of the purposes for which air-pump in condensing steam-engines was provided, a from which it took its name, was to draw off this air. If, however, a tubular condenser could be made to act v the necessary efficiency, no injection water would be introduced for condensation, and the pump would have no other duty except to remove the small quantity of water produced by the condensed steam. That water being subsequently carried back to the boiler by the feed-pumps, a constant system of circulation would be maintained, and the boiler would never require any fresh supply of water, except what might be necessary to make good the waste by leakage a other causes. This contrivance has been of late years revived by Samuel Hall of Basford, near Nottingham, with a view,, supersede in marine engines the necessity of using sea-water in the boilers. Mr. Hall proposes to make marine boiler with fresh water to condense the steam without injection a tubulated condenser, and to provide by the distillation of sea-water the small quantity of fresh water which would -necessary to make good the waste. These condensers have been introduced into several steam-vessels: in some they have been continued, and in others abandoned, and various opinions are entertained of their efficacy. I have not been able to obtain the results of any satisfactory experiments them, and cannot therefore form a judgment of their usefulness. Mr. Watt abandoned these condensers from find ii that the condensation of the steam was not sufficient sudden, and that consequently at the commencement of the stroke the piston was subject to a resistance which injuriously diminished the amount of the moving power, whereas condensation by jet was almost instantaneous, and the efficiency of the piston throughout the entire stroke was more uniform. Mr. Watt also found that a fur collected around the tubes of the condenser, so as to obstruct the free passage of heat from the steam to the water of the cold cistern; and that, consequently, the efficiency of the condenser was gradually impaired and could only be restored by frequent cleansing. It is stated by Mr. Hall that a vacuum is preserved in his condensers as perfect as that which is maintained in the ordinary condensers by injection. It is objected, on the other hand, that without the injection water and the air which accompanies it being introduced into his condensers, Mr. Hall uses as large and powerful an air-pump as those which are used in engines of equal power condensing by injection; that, consequently, the vacuum which is maintained is produced, not as it ought to be altogether by the condensation of steam, but by the air-pump drawing off the uncondensed steam. To whatever extent this may be true, the efficacy of the machine, as indicated by the barometer-gauge, is only apparent; since as much power is necessary to pump away any portion of uncondensed vapour as is obtained by the vacuum produced by the absence of that vapour. A tubular condenser of the form proposed by Mr. Hall is represented in fig. 126.; a is the upper part of the condenser to which steam is admitted from the slide after having worked the piston; k is the section of a thin plate, forming the top of - the condenser, perforated with small holes, in which the tubes are inserted so as to be steam-tight and watertight.

Fig. 126

Water is admitted to flow around these tubes between the top k and the bottom d of the condenser, so as to keep them constantly at a low temperature. The steam passes from a through the tubes to the lower chamber f of the condenser, where it is reduced to water by the cold to which it has been exposed. A supply of cold water is constantly pumped through the condenser, so as to keep the tubes at a low temperature. The air-pump g is of the usual construction, having valves in the piston opening upwards, and similar valves in the cover of the pump Also opening upwards. The water formed by the condensed steam in f is drawn through the foot-valve, and after passing through the piston valves, is discharged by the upstroke of the piston into the hot well. Any air, or other permanent gas, which may be admitted by leakage through the tubes of the condenser, or by any other means, is likewise drawn out by this pump, and when drawn into the hot well is carried from thence to the feeding apparatus of the boiler, to which it is transferred by the feed-pump. A provision is likewise made by which the steam escaping at the safety-valve is condensed and carried away to the feeding cistern. (214.) One of the remedies proposed for the evil consequences arising from incrustation is the substitution of copper for iron boilers. The attraction which produces the adhesion of the calcareous matter held in solution by salt water to the surface of iron has no existence in copper, and all the saline and other alkaline matter precipitated in the boiling water in copper boilers is suspended in a loose form, and carried off by the process of blowing out. Besides the injury arising from the deposition of salt and the incrustation on the inner surface of boilers, an evil of a formidable kind attends the accumulation of soot mixed with salt in the flues, which proceeds from the leaks. In the seams of the boiler there are numerous apertures, of dimensions so shall as to be incapable of being rendered stanch by any practicable means, through which the water within the boiler filters, and the salt which it carries with it mixes with the soot, forming a compound which rapidly corrodes the boilers. This process of corrosion in the flues takes place not less in copper than in iron-boilers. In cleansing the flues of a copper boiler, the salt and soot which was thrown out upon the iron-plates which formed the flooring of the engine-room, having remained there for some time, left behind it a permanent appearance of copper on the iron flooring, arising from the precipitation of the copper which bad combined with the soot and salt in the flues.* In this case the leaks from whence the salt proceeded were found, on careful examination, so unimportant, that the usual means to stanch them could not be resorted to without the risk of increasing the evil. (215.) In the application of the steam-engine to the propulsion of vessels in voyages of great extent, the economy of fuel acquires an importance greater than that which appertains to it in land-engines, even in localities the most removed from coal mines, and where its expense is greatest. The practical limit to steam-voyages being determined by the greatest quantity of coals which a steam-vessel can carry, every expedient by which the efficiency of the fuel can be increased becomes a means, not merely of a saving of expense, but of ark increased extension of steam-power to navigation. Much attention has been bestowed on the augmentation of the duty of engines in the mining districts of Cornwall, where the question of their efficiency is merely a question of economy, but far greater care should be given to this subject when the practicability of maintaining intercourse by steam between distant points of the globe Will perhaps depend on the effect produced by a given quantity of fuel. So long as steam-navigation was confined to river and channel transport, and to coasting voyages, the speed of the vessel was a paramount consideration, at whatever expenditure of fuel it might be obtained; but since steam-navigation has been extended to ocean-voyages, where coals must be transported sufficient to keep the 'engine in operation for a long period of time without a fresh relay, greater attention has been bestowed upon the means of economising it. Much of the efficiency of fuel must depend on the management of the fires, and therefore on the skill and care of the stokers. Formerly the efficiency of firemen was determined by the abundant production of steam, and so long as the steam was evolved in superabundance, however it might have blown off to waste, the duty of the stoker was considered as well performed. The regulation of the fires according to the demands of the engine were not thought of, or whether much or little steam was wanted, the duty of the stoker was to urge the fires to their extreme limit. Since the resistance opposed by the action of the paddle wheels of a steam-vessel varies with the state of the weather, the consumption of steam in the cylinders must undergo a corresponding variation; and if the production of steam in the boilers be not proportioned to this, the engines will either work with less efficiency than they might do under the actual circumstances of the weather, or more steam will be produced in the boilers than the cylinders can consume, and the surplus will be discharged to waste through the safety-valves. The stokers of the marine engine, therefore, to perform their duty with efficiency, and obtain from the fuel the greatest possible effect, must discharge the functions of a self-regulating furnace, such as has been already described: they must regulate the force of the fires by the amount of steam which the cylinders are capable of consuming, and they must take care that no unconsumed allowed to be carried away from the ash-pit. (2 1 6.) Until within a few years of the present time the heat radiated from every part of the surface of the boiler was allowed to go to waste, and to produce injurious effects on those parts of the vessel to which it was transmitted. This evil, however, has been lately removed by coating the boilers, steam pipes , &c. of steam-vessels with felt, by which the escape of heat from the surface of the boiler is very nearly, if not altogether, prevented. This felt is attached to the boiler-surface y a thick covering of white and red lead. This expedient was first applied in the year 1818 to a private steam-vessel of Mr. Watt called the Caledonia, and it was subsequently tried later in another vessel, the machinery of which was constructed at Soho, called the Tames Wait. The economy of fuel depends in a considerable degree on the arrangement of the furnaces, and the method of feeding them. In general each boiler is worked by two or more furnaces communicating with the same system of flues. While the furnace is fed, the door being open, a stream of cold air ashes in, passing over the burning fuel and lowering the temperature of the flues: this is an evil to be avoided. But, on the other hand, if the furnaces be fed at distant intervals, then each furnace will be unduly heaped with fuel, a great quantity of smoke will be evolved, and the combustion of the fuel will be proportionally imperfect. The process of cocking in front of the grate, which would insure a complete combustion of the fuel, has been already described (147.). A frequent supply of coals, however, laid carefully on the front I art of the grate, and gradually pushed backwards as each I fresh feed is introduced, would require the fire-door to be frequently opened, and cold air to be Admitted. It would also require greater vigilance on the part of the stokers than an generally be obtained in the circumstances in which they fork. In steam-vessels the furnaces are therefore fed less 'frequently, fuel introduced in greater quantities, and a less perfect combustion produced. When several furnaces are constructed under the same boiler, communicating with the same system of flues, the process of feeding, and consequently opening one of them, Obstructs the due operation of the others, for the current of cold air which is thus admitted into the flues checks the draft and diminishes the efficiency of the furnaces in operation. It was formerly the practice in vessels exceeding one hundred horsepower, to place four furnaces under each boiler, communicating with the same system of flues. Such an arrangement was found to be attended with a bad draft in the furnaces, and therefore to require a greater quantity of heating surface to produce the necessary evaporation. This entailed upon the machinery the occupation of more space in the vessel in proportion to its power; it has therefore been more recently the practice to give a separate system of flues to each pair of furnaces, or, at most, to every three furnaces. When three furnaces communicate with a common flue, two will always be in operation, while the third is being cleared out; but if the same quantity of fire were divided among two furnaces, then the clearing out of one would throw out of operation half the entire quantity of fire, and during the process the evaporation would be injuriously diminished. It is found by experience, that the side plates of furnaces are liable to more rapid destruction than their roofs, owing, probably, to a greater liability to deposit. Furnaces, therefore, should not be made narrower than a certain limit. Great depth from front to back is also attended with practical inconvenience, as it renders firing tools of considerable length, and a corresponding extent of stoking room necessary. It is recommended, by those who have had much practical experience in steam-vessels, that furnaces six feet in depth from front to back should not be less than three feet in width, to afford means of firing with as little injury to the side plates a in the condition necessary as possible, and of keeping the fire tops of for the production of the greatest effect. T the furnaces almost never decay, and seldom are subject to an alteration of figure, unless the level of the water be allowed to fall below. A form of marine engine was some years since processing much posed and patented by Mr. Thomas Howard, possessing novelty temperature varying from 4000 to 500o. The surface exposed to the fire was computed at three fourths of a square foot for each horsepower. The upper surface of the mercury was covered by a very thin plate of iron in contact with it, and so contrived as to present about four times as much Surface a& that exposed beneath the fire. Adjacent to this a vessel of water was placed, maintained nearly at the boiling point, and communicating by a nozzle and valve with the chamber immediately above the mercury. At intervals corresponding to the motion of the piston a small quantity of water was injected from this vessel, and thrown upon the plate of iron resting upon the hot mercury. From this it received not only the heat necessary to convert it into common steam, but to give it the qualities of highly superheated steam. In fact, the steam thus produced had a temperature considerably above that which corresponded to its pressure, and was, therefore, capable of being deprived of more or less of its heat without being condensed. (94.) The quantity of water injected into the steam-chamber was regulated by the power at which the engine was intended to be worked. The fire was supplied with air by a blower subject to exact regulation. The steam thus produced was conducted to a chamber surrounding the working cylinder, and this chamber itself was enclosed by another space through which the air from the furnace passed before it reached the. flue. By this contrivance the air imparted its redundant heat to the steam, a.% the latter passed to the cylinder, and raised its temperature to about 4,NG, the pressure, however, not exceeding 25 lb. per square inch. The valves, governing the admission of steam to the piston, were adapted for expansive action.

The vacuum on the opposite side was maintained by condensation in the following manner: - The condenser was a copper vessel placed in a cistern of cold water, and the steam was admitted to it from the cylinder by an eduction pipe in the usual way. A jet was introduced from an adjacent vessel filled with distilled water, and the condensing water and condensed steam were pumped from the condenser as in common engines. The warm water thus pumped out of the R H and ingenuity, and having pretensions to a very extraordinary economy of fuel, in addition to the advantages claimed by Mr. Hall. In Mr. Howard's engines, the steam, as in Mr. Hall's, is constantly reproduced from the same water, so that pure or distilled water may be used; but Mr. Howard dispenses altogether with the use of a boiler. A quantity of mercury is placed in a shallow wrought-iron vessel over a coke fire, by which it is maintained at a temperature varying from 400 to 500. The surface exposed to the fire was computed at three fourths of a square foot for each horsepower. The upper surface of the mercury was covered by a very thin plate of iron in contact with it, and so contrived as to present about four times as much Surface a& that exposed beneath the fire. Adjacent to this a vessel of water was placed, maintained nearly at the boiling point, and communicating by a nozzle and valve with the chamber immediately above the mercury. At intervals corresponding to the motion of the piston a small quantity of water was injected from this vessel, and thrown upon the plate of iron resting upon the hot mercury. From this it received not only the heat necessary to convert it into common steam, but to give it the qualities of highly superheated steam. In fact, the steam thus produced had a temperature considerably above that which corresponded to its pressure, and was, therefore, capable of being deprived of more or less of its heat without being condensed. (94.) The quantity of water injected into the steam-chamber was regulated by the power at which the engine was intended to be worked. The fire was supplied with air by a blower subject to exact regulation. The steam thus produced was conducted to a chamber surrounding the working cylinder, and this chamber itself was enclosed by another space through which the air from the furnace passed before it reached the. flue. By this contrivance the air imparted its redundant heat to the steam, a.% the latter passed to the cylinder, and raised its temperature to about 4,NG, the pressure, however, not exceeding 25 lbs. per square inch. The valves, governing the admission of steam to the piston, were adapted for expansive action.

The vacuum on the opposite side was maintained by condensation in the following manner: - The condenser was a copper vessel placed in a cistern of cold water, and the steam was admitted to it from the cylinder by an eduction pipe in the usual way. A jet was introduced from an adjacent vessel filled with distilled water, and the condensing water and condensed steam were pumped from the condenser as in common engines. The warm water thus pumped out of the condenser was drawn through 9. copper worm" carried with many coils through a cistern of cold water, so that when it arrived at the end of this pipe it was reduced nearly to the temperature of the atmosphere. The pipe was thus brought to the vessel of distilled water already mentioned, and the water supplied by it replaced. The water admitted to the condenser through the condensing jet being purged of air, a small air-pump was sufficient, since it had only to exhaust the condenser and tubes at starting, and to remove the air which might be admitted by leakage. Mr. Howard stated that the condensation took place as rapidly and perfectly as in the best engines of the common kind.

An engine of this construction was in the spring of 1835 Placed in the government steamer called the Comet. It was stated, that though the machinery was not advantageously constructed, a part of the engine being old, and not made especially for a boiler of this kind, the vessel performed a voyage from Falmouth to Lisbon, in which the consumption of fuel did not exceed a third of her former consumption when worked by Boulton and Watt's engines, the former consumption of coals being about eight hundred pounds per hour, and the consumption of Mr. Howard's engine being less than two hundred and fifty pounds of coke per hour.

The advantages claimed for this contrivance were the following: first, the small space and weight occupied by the machinery-, arising from the absence of a boiler; second, the diminished consumption of fuel; third, the reduced size of the flues; fourth, the removal of the injurious effects arising from deposit and incrustation; fifth, the absence of smoke. (218.) The method by which the greatest quantity of practical effect can be obtained from a given quantity of fuel, must, however, mainly depend on the extended application of the expensive principle. This has been the means by which an extraordinary amount of duty has been obtained from the Cornish engines. The difficulty of the application of this principle in marine engines has arisen from the objections entertained in Europe to the use of steam of high pressure under the circumstances in which the engine must be worked at sea. To apply the expansive principle, it is necessary that the moving power at t of the stroke shall considerably exceed the resistance, its force being gradually attenuated till the completion of the stroke, when it will at length become less than the resistance. This condition may, however, be attained with steam of limited pressure, if the engine be constructed with a sufficient quantity of piston-surface. This method of rendering the expansive principle available at sea, and compatible with low-pressure steam, has recently been brought into operation by Messrs. Maudslay and Field. Their improvement consists in adapting two steam-cylinders in one engine, in such a manner that the steam shall act simultaneously on both pistons, causing them to ascend and descend together. The piston-rods are both attached to the same horizontal cross-head, whereby their combined action is applied to one crank by means of a connecting rod placed between the pistons. A section of such an engine, made by a plane passing through the two piston-rods P P' and cylinders, is represented in fig. 127. The piston-rods are attached to a cross-head c,

Fig. 127

and descends with them, This cross-head drives upwards and downwards on axis D, to which the lower end of the connecting rod v is attached. The other end of the connecting rod drives the crank-pin F, and imparts revolution to the paddle-shaft a. A rod x conveys motion by means of a beam I to the rod K of the air-pump E. Connected with this, and in the same patent, another improvement is included, consisting of the application of a hollow wrought-iron framing carrier 1 across tile vessel above the machinery, to support the whole of the bearings of the crankshaft. A plan of this, including the cylinders and paddlewheel, is represented in fig. 128.

Fig. 128

The advantages proposed by these improvements are simplicity of construction, more direct action on the crank, economy of space and weight of material, combined with increased area of the piston, whereby a given evaporating power of the boiler is rendered productive, by extended application of the expansive principle, of a greater moving power than in former arrangements. Consequently, under like circumstances, greater power and economy of fuel is obtained, with the further advantage at sea in which the engine is -reduced in its speed, either by the vessel being deeply laden with coal, as is the case at the commencement of a long sea voyage, or by head winds, more steam maybe given to the cylinders, and consequently more speed imparted to the vessel, all the steam produced in the boiler being usefully employed. (220.) Another improvement, having the same objects, and analogous to the preceding, has likewise patented by Messrs. Maudslay and Field. This consistent head options offer a cylinder of greater diameter, having two piston-rods P V, u represented in)Fg.129., of considerable length, connected at the top by a cross-head c. From this cross-head is carried downwards the connecting rod D, which drives the crank-pin z, and thereby works the paddle-shaft s. In this case the paddle-shaft is extended immediately above the piston, and the double piston-rod has sufficient length to be above the paddle-shaft when the piston is at the bottom of its stroke This improvement is intended to be applied more particularly for engines for river navigation, the advantages resulting from (221.) (223.) it being that a paddle-shaft placed at a given height from the bottom of the vessel will be enabled to receive a longer stroke of piston than by any other arrangement now in use.

Fig. 129


A more compact and firm connection of the cylinder with the crank-shaft bearings is effected by it, and a cylinder of much greater diameter may be applied by which the expansive action of steam may be more fully brought into play; and a more direct action of the steam-power on the crank with a less weight of materials and a greater economy of space may be obtained than by any of the arrangements of marine engines hitherto used. (221.) Mr. Francis Humphrys has obtained a patent for a form of marine engine, by which some simplification of the machinery is attained, and the same power comprised within more limited dimensions. In this engine there is attached to the piston of the cylinder, instead of a piston-rod, a hollow casing D D (fig. 130.), which moves through a stuffing-box G, constructed in a manner similar to the stuffing-box of a piston-rod. In the figure, this casing is presented in section, but its form is that of a long narrow slit, or opening, rounded at either end as exhibited in the plan (fig.131) of the cylinder cover. The crank c is driven by the other end of the connecting rod H, the crank-shaft being immediately above the centre of the piston and the connecting rod passing through the oblong opening D, and descending into the hollow piston-rod it is attached to an axis I at the bottom of the piston. A box or cover K K encloses the crosspiece or axis I with its bearings, and is attached so as to be steam-tight to the bottom of the piston.

Fig. 130

A hollow space L is cut in the bottom of the cylinder for the reception of the box K, when the piston is at the bottom of the cylinder. By this arrangement the force by which the piston is driven in its ascent and descent is communicated to the connecting rod, not, as usual, through the intervention of a piston-rod, but directly from the piston itself by the cross-pin I, from thence to the crank c, which it drives without the intervention of beams, cross-heads, or any similar appendage. The slide-valves regulating the admission and eduction of steam are represented at a; the rod of the air-pump is shown at d, being worked by a crank placed on the centre of the great crank shaft.* (222.) To obtain from the moving power its full amount of mechanical effect in propelling the vessel, it would be necessary that its force should propel, by constantly acting against the water in a horizontal direction. and with a motion contrary to the course of the vessel. No system of mechanical propellers has, however, yet been contrived capable of perfectly accomplishing this. Patents have been granted for many ingenious mechanical combinations to impart to the propelling surfaces such angles as appeared to the respective contrivers most advantageous. In most of these mechanical complexity has formed a fatal objection. No part of the machinery of a steam-vessel is so liable to become deranged at sea as the paddlewheels; and, therefore, that simplicity of construction which is compatible with those repairs which are possible on such emerges is quite essential for safe practical use. The ordinary paddlewheel, as has been already stated, is a wheel revolving upon a shaft driven by the engine, and carrying upon its circumference a number of flat boards, called paddle-boards, which we secured by nuts and braces in a fixed position is such that the planes of the paddle-boards diverge nearly from the centre of the shaft on which the wheel turns. The consequence of this arrangement is that each paddle-board can only act in that direction which is most advantageous for the propulsion of the vessel when it moves near the lowest point of the water. In fig.132 let o be the shaft on which the common paddle-wheel revolves; the position of the paddle boards are represented at A, b, c, &c. ; x, T represents the water line, the course of the vessel being supposed to be from x to Y ; the arrows represent the direction in which the paddlewheel revolves. The wheel is immersed to the depth of the lowest paddle-board, since a ]en degree of immersion would render a portion of the surface of each paddle-board mechanically useless. In the position A, the whole force of the paddle board is efficient for propelling the vessel ; but as the paddle enters the water in the position H, its action upon the water, not being horizontal, is only partially effective for propulsion: a part of the force which drives the paddle is in depressing the water, and the remainder in driving it contrary to the course of the vessel, and, therefore, by its reaction producing a certain propelling effect. The tendency, however, of the paddle entering the water at ii, in to form a hollow or trough, which the water, by its ordinary property, has a continual tendency to fill up. After passing the lowest Point A, " the paddle approaches the position is, where it emerges from the water, its action again becomes oblique, a part only having a propelling effect, and the remainder having a tendency to raise the water, and throw up a wave and spray behind the paddlewheel.

Fig. 132

It is evident that the more deeply the paddlewheel becomes immersed, the greater, will be the proportion of the propelling power that wasted in elevating and depressing the water; and if the wheel were immersed to its axis, the whole force of the paddle-boards, on entering and leaving the water, would be lost, no part of it having a tendency to propel. If a still deeper immersion take place, the paddle-boards above the axis, would have a tendency to retard the course of the vessel. When the vessel is, therefore, in proper trim, the immersion should not exceed nor for short of the depth of the lowest paddle; but for various reasons it is impossible in practice to maintain this fixed immersion: the agitation of the surface of the sea, causing the vessel to roll, will necessarily produce a great variation in the immersion of the paddlewheels, one becoming frequently immersed to its axle, while the other is raised altogether out of the water. Also the draught of water of the vessel is liable to change, by the variation in her cargo; this will necessarily happen in steamers which take long voyages. At starting they are heavily laden with fuel, which as they proceed is gradually consumed, whereby the vessel is lightened. (223) To remove this defect, and economics as much as possible the propelling effect of the paddle-boards, it would them that they may be necessary so to construct enter and leave the water edgeways, or as nearly so as possible; such an arrangement would be, in effect, equivalent to the process called feathering, as applied to oars. Any mechanism which would perfectly accomplish this would cause the paddles to cause, and would very nearly remove work in almost perfect silence the inconvenient and injurious vibration which is produced by the action of the common paddles. But the construction of feathering paddles is attended with great difficulty, under the peculiar circumstances in which such wheels work. Any mechanism so complex that it could not be easily repaired when deranged, with such engineering implements and skill as can be obtained at sea, would be attended with great objections; and the efficiency of its propelling action would not compensate for the dangers which must attend upon the helpless state of a sterner, deprived of her propelling agents.

Feathering paddle-boards must necessarily have a motion independently of the motion of the wheel, since any fixed position which could be given to them, though it might be most favourable to their action in one position would not be so in their whole course through the water. Thus the paddle board when at the lowest point should be in a vertical position, or so placed that its plane, if continued upwards, would pass through the axis of the wheel. lit other positions, however, as it passes through the water, it should present its upper edge, not towards the wheel, but towards a point above the highest point of the wheel. The precise point to which the edge of the paddle-board should be directed is capable of mathematical determination. But it will vary according to circumstances, which depend on the motion of the vessel. The progressive motion of the vessel, independently of the wind or current, must obviously be slower than the motion of the paddle boards round the axle of the wheel; since it is by the difference of these velocities that the reaction of the water is produced by which the vessel is propelled. The proportion, however, between the progressive speed of the vessel and the rotative speed of the paddle boards is not fixed: it will vary with the shape and structure of the vessel, and with its depth of immersion ; nevertheless it is upon this proportion that the manner in which the paddle boards should shift their position must be determined. If the progressive speed of the vessel were nearly equal to the rotative speed of the paddle-boards, the latter should so shift their position that their upper edges should be presented to a point very little above the highest point of the wheel. This is a state of things which could only take place- in the case of a steamer. of a small draught of water, scallop-shaped, and so constructed as to suffer little resistance from the fluid. On the other hand, the. greater the depth of immersion, and the less fine the lines of the vessel, the greater will be the resistance in passing through the water, and the greater will be the proportion which the rotative speed of the paddle-boards will bear to the progressive speed of the vessel. In this latter case the independent motion of the paddle boar should be such that their edges, while in the water, be presented towards a point considerably above the highest point of the paddle wheel. A vast number of ingenious mechanical contrivances have been invented and patented for accomplishing the object just explained. Some of these have failed from the circumstance of their inventors not clearly understanding what precise motion it was meant to impart to the paddle board: others by which way for the paddle wheel with movable paddles, which patent granted to Elijah Gal was purchased by Mr. William Morgan, who made various alterations in the mechanism, not very materially departing from the principle of the invention. This paddle wheel is represented in fig. 133. The contrivance may be shortly stated to consist in causing the wheel which began the paddles to revolve on one centre, and the radial arms which move the paddles to revolve on another centre. A B C D E F 0 If I X L be the polygonal circumference of the paddle wheel, formed of straight bars, secured connected together at the extremities of the spokes or radii of the wheel which turns on the shaft which is worked by the engine; the centre of this wheel being at O. So far this wheel is similar to the common paddle wheel; but the paddle boards are not, as in the common wheel, fixed at A B C, so as to be always directed to the centre u, but so placed that they are capable of turning on an axis which are always horizontal, so that they can take any angle with respect to the water which may be given to them. From the centre, or the line joining the pivots on which these paddle-boards turn, there proceed short arms K, firmly fixed to the paddle boards at an angle of about 120'. On a motion given to this arm v., it will therefore give a corresponding angular motion 0 the paddle board so as to make it turn on its pivots. At the extremities of the several arms marked x is a pin or pivot, which the extremities of the radial arms L are severally,attached, so that the angle between each radial L and the short paddle-arm x is capable of being changed by any force imparted to L; the radial arms are connected at the other lid with a centre, round which they are capable of revolving. Now, since the points A B C, &c., which are the pivots on which the paddle-boards turn, are moved in the circumference I f a circle, of which the centre is o, they are always at the same distance from that point; consequently they will continually vary their distance from the other centre P. Thus, when a paddle-board arrives at that point of its revolution at which the centre round which it revolves lies precisely be. I faced it to the centre 0, its distance from the former centre 1 less than from any other position. As it departs from that outside, its distance from that centre gradually increases until it ,arrives at the opposite point of its revolution, where the centre o is exactly between it and the former centre then the distance of the paddle-board from the former centre is greatest.

Fig. 133

This constant change of distance between each paddle -board and the centre P is accommodated by the variation of the angle he short paddle-board arm K; between the radial arm L and t -as. the paddle-board approaches the centre, r this gradually diminishes; and as the distance of the paddle-board increases, the angle is likewise augmented. This change in the magnitude of the angle, which thus accommodates the varying position of the paddle-board with respect to the centre P, will he observed in the figure. The paddle-board D is nearest to P; and it will be observed that the angle contained between L and K in there very acute; at B the angle between L and x is to a right angle; increases, but is still acute ; at G it increases at H it becomes obtuse; and at v., where it is most distant from the centre r, it becomes most obtuse. It again diminishes, and becomes a right angle between A and B. Now 14' this continual shifting of the direction of the short arm Y. is necessarily accompanied by an equivalent change of position in the paddle-board to which it is attached and the position of the second centre P is, or may be, so adjusted that this paddle-board, as it enters the water and emerges from it, shall be such as shall be most advantageous for propelling the vessel, and therefore attended with less of that vibration which arises chiefly from the alternate depression and elevation of the water, owing to the oblique action of the paddle- (225.) In the year 1833, Mr. Field, of the firm of Maudslay and field, constructed a paddle wheel with fixed paddle-boards, but each board 'being divided into several narrow slips arranged one a little behind the other, u represented in fig. 134. These divided bows he proposed to arrange in such cylindrical curves that they must all enter the 135. water at the same place in immediate succession, avoiding the shock produced by the entrance of the common board. These split paddle-boards are as efficient in propelling when at the lowest point as the common paddle-boards, and when they emerge the water escapes simultaneously front each narrow board, and is not thrown up, as is the case with common paddle-

Fig. 134

The theoretical effect of this wheel is the "me as that of the common wheel, and experience alone, the result of which has not yet been obtained, can prove its efficiency. The number of bars, or separate parts into which each paddle-board is divided, has been very various. When first introduced by Mr. Galloway each board was divided into six or seven parts-. this was subsequently reduced, and in the more recent wheels of this form constructed for the government vessels the paddle-boards consist only of two parts, coming as near to the common wheel as is possible, without altogether abandoning the principle of the split paddle. (226.) To obtain an approximate estimate of the extent to which steam-power is applicable to long sea-voyages, it would be necessary to investigate the mutual relation which, in the existing state of this application of steam-power, exists between the capacity or tonnage of the vessel, the magnitude, weight, and power, of the machinery, the available stowage for fuel, and the average speed attainable in all

Field did not persevere in its use at the time he invented it. It ban, however, been more generally adopted since the date of Galloway' weathers, as well as the general purposes to which the vessel is to be appropriated, whether for the transport Of goods or merchandise, or merely for dispatches and passengers, or for combined. That portion of the capacity of the both of these to the moving power consists of vessel which is appropriated the fuel. The space occupied by the machinery and distribution of it between these must mainly depend on the without length of the voyage which the vessel must receiving a fresh supply of coal. if the trips be short, and frequent relays of fuel can be obtained, then the space allotted to the machinery may bear a greater proportion to that assigned to the fuel; but in proportion as each uniform of interrupted stage of the voyage is increased, a greater s a y less space left will be necessary, and a proportion for the machinery. Other things being the same, therefore steam-vessels intended for long sea-voyages must be less powerful in proportion to their tonnage. It will be apparent that every improvement which takes place in the application of the steam-engine to navigation win Me all these data on which shall an investigation must depend Every increased efficiency of fuel, from whatever cause it may be derived, will either increase the useful tonnage of the vessel, or increase the length of voyage of which it is capable. Various improvements have been and are still in progress, by which the efficiency has undergone continual augmentation, and voyages may now be accomplished with moderate economy and profit, to which a few years since marine engines could not be applied with permanent advantage. The average speed of steam-vessels has undergone a gradual increase by such improvements. During the four years ending June, 1834, it was found that from fifty-one voyages the average rate of steaming obtained made by the Admiralty steamers between Falmouth and Corfu, exclusive of stoppages, was seven miles and a quarter an hour direct distance between port and port. The vessels which performed this voyage varied from 350 to 700 tons measured burden, and were provided with engines varying from 109 to 200 horsepower, with stowage for coals varying from 80 to 240 tons. The proportion of the power to the

A linkage varied from one horse to three tons to one horse to many have already. stated that the nominal horsepower is extremely indefinite; and if, as is now customary in a longer class of voyages, the steam be worked exponentially then the nominal power almost ceases to have any C, higher relation to the actual performance of the vessel. It is usual to calculate the horsepower by assuming a firm pressure of steam upon the piston, and, consequently, I excluding the consideration of the effect of expansion. ;The most certain test of the amount of mechanical power asserted by the machinery would be obtained from the quality of water actually transmitted in the form of steam from II c boiler to the cylinder. But the effect of this would also be influenced by the extent to which the expansive principle has been brought into operation. From the reported performances of the larger class of high action ships within the last few years, it would appear that average speed has been consistent since the estimate L above mentioned, which was obtained in 1834; and on the consumption of fuel with the actual performance, it would appear that the efficiency of fuel has also been considerably augmented. No extensive course of accurate lists or observations have, however, been obtained in which correct inferences may be drawn. Of the probable things steam navigation, in its present state, is being extended. The jealousy of rival companies is obstructing the junctions of those who, solicitous swore. for the general advancement of the art than for the success of individual enterprises, have directed their attention to this question ; and it is hardly to be expected that sufficiently correct and extensive data call be obtained for this purpose. (227.) Increased facility in the extension and application of steam-navigation is expected to arise from tile substitution of iron for wood, in die construction of vessels. Therefore iron steamers have been chiefly confined to river-navigation; but there appears no sufficient reason why their use should be thus limited. For sea-voyages they offer many advantages; they are not half the weight of vessels of equal tonnage constructed of wood; and, consequently, with the same tonnage they will have less draught of water, and therefore less resistance to the propelling power; or, with the same draught of water and the same resistance, they will carry a proportionally heavier cargo. The nature of their material renders. them more stiff and unyielding than timber; and they do not suffer that effect which is called hollow, which arises from a slight alteration which takes place in the figure of a timber vessel in rolling, accompanied by an alternate opening and closing of the seams. Iron vessels have the further advantage of being more proof against fracture upon rocks. If a timber vessel strike, a plank is broken, mid a chasm opened in her many times greater than the point of rock which produces the concussion. If an iron vessel strike, she will either severely receive a blow, or be pierced by a hole equal in size to the point of rock which she encounters. Some examples of the strength of iron vessels were given by Mr. Macgregorard, in his evidence before the Committee of the Commissioners on Steam Navigation, among which the following may be mentioned - - iron vessel, called the ALBUITKAII, ill One of their experimental trials got aground, and lay upon her anchor: in a wooden vessel the anchor would probably have pierced her bottom ; in this case, however-, tile bottom was only damaged. All iron vessel, built for the Irish Inland Navigation Company, works being, towed across Lougli Derg it, it gale of wind, when the towing rope broke, and she was driven upon rocks, on which site bumped for a considerable time without any injury. A wooden vessel would in this case five gone to pieces. A further advantage of iron vessels ,which in warm climates is deserving of consideration is their better coolness and perfect freedom from vermin. Iron steam-vessels on a very large scale are now in preparation in the ports of Liverpool and Bristol, intended for long sea-voyages. The largest vessel of this description which has yet been projected is stated to be in preparation or the voyage between Bristol and New York, by the company any who have established the steamship called the Great Eastern, plying between these places.

Several projects for the extension of steam-navigation to voyages of considerable length have lately been entertained both by the public and by the legislature, and have imparted sincere attempt to improve steam-navigation increased interest. A committee of the House of Commons collected evidence and made a report in the last session in favour of an experiment to establish a line of steam-communication between Great Britain and India. Two routes have been suggested by each committee, each being a continuation of the line of Admiralty steam-packets already established to Malta I the Ionian Isles. One of the routes proposed is through the Red Sea, and across the Indian Ocean to Bombay, some Of the older presidencies ; the other across the north to , banks of the Euphrates, by that river to the Persian Gulf, and from thence to Bombay. Each of these routes will be attended with peculiar difficulties, and in a long sea-voyage will be encountered. In the route by the Red Sea it is proposed to establish relations between Malta and Alexandria (eight hundred and eighty miles). A steamer of four hundred tons' burden and two hundred horsepower would perform this voyage, upon average of all weather incident to the situation, in from five to six days, consuming ten tons of coal per day. But it is probable that it might be found more advantageous to establish a higher ratio between the power and the tonnage. From Alexandria the transit might be effected by land across isthmus to Suez - a journey of from four to five days by caravan and camels; or the transit Ought be made either by land or water from Alexandria to Cairo, a distance of one hundred and seventy-three miles; and from-Cairo to Suez, ninety-three miles, across the desert, in about- five days. At Suez would be a station for steamers, and the Red Sea would be traversed in three runs or more. If necessary, stations for coals might be established at Cosseir, Judda, Mocha, and finally at Aden or at Socatra - an island immediately beyond the mouth of the Red Sea, in the Indian Ocean;. the run from Suez to Cosseir would be three hundred miles - somewhat more than twice the distance from Liverpool to Dublin. From Cosseir to Judda, four hundred and fifty miles; from Judda to Mocha, five hundred and seventeen miles; and from Mocha to Socatra, six hundred and forty-two miles. It is evident that all this would, without difficulty, in the most powers of unfavourable weather, fall within the present steam-navigation. If the terminus of the passage be Bombay, the run from Socatra to Bombay will be twelve hundred miles, which would be from six to eight days' steaming. The whole passage from Alexandria to Bombay, allowing three days for delay between Suez and Bombay, would be twenty-six days; the time from Bombay to Malta would therefore be about thirty-three days; and adding fourteen days to for the transit from Malta to England, we should -seven days from London to Bombay, or have a total of forty loft about seven weeks.

If the terminus proposed were - Calcutta, the course from Socratra would be one thousand two hundred and fifty miles southeast to the Maldives, where a station for coals would be established. This distance would be equal to that from Socatra to Bombay. From the Maldives, a run hundred miles would reach the southern point of Ceylon, called the Point de Galle, which is the best harbour (Bombay excepted) in British India: from the Point de Galle, a run of six hundred miles will reach Madras, and from Madras to Calcutta would be a run of about six hundred unites. The voyage from London to Calcutta would be performed in about sixty days.

At a certain season of the year there exists a powerful physical opponent to the transit from India to Suez: frontthe middle of June until the end of September, the southwest monsoon blows with unabated force across the Indian Ocean, and more particularly between Socatra and Bombay. This wind is so violent as to leave it barely possible for the most powerful steam-packet to make head against it, and the voyage could not be accomplished without serious wear and tear upon the vessels during these months. The attention of parliament has therefore been directed to another line of communication, not liable to this difficulty-. it is proposed to establish a line of steamers from Bombay through the Persian Gulf to the Euphrates. The run from Bombay to a place called Muscat, on the southern shore of the gulf, would be eight hundred and forty miles in a northwest direction, and therefore not opposed to the south-west monsoon. From Muscat to Bassidore, a point upon the northern coast of the strait at the mouth of the Persian Gulf, would be a run of two hundred and fifty-five miles ; from Bassidore to Bushire, another point on the eastern coast of the Persian Gulf, would be a run of three hundred miles ; and from Bushire to the mouth of the Euphrates, would be one hundred and twenty miles. It is evident that the longest of these runs would offer no more difficulty than the passage from Malta to Alexandria. From Bussora, near the mouth of the Euphrates, to Bir, a town upon its left bank near Aleppo, would be one thousand one hundred and forty-three miles, throughout which there are no physical obstacles to the river-navigation which may not be overcome. Some difficulties arise from the wild and savage character of the tribes who occupy its banks. It is, however, thought that by proper measures, and securing the cooperation of the pacha of Egypt, any serious obstruction from this cause may be removed. From Bir, by Aleppo, to Scanderoon, a port upon the Mediterranean, opposite Cyprus, is a laid-journey, Raid to be attended with some difficulty, but not of great length; and from Scanderooti to Malta is about the same distance as between the latter place and Alexandria. It is calculated that the time from London to Bombay by the Euphrates- supposing the passage to be successfully established-would be a few days shorter than by Egypt and the Red Sea. Whichever of these courses may be adopted, it is clear that the difficulties, so far as the powers of the steam engine are concerned, lie in the one case between Socatra and Bombay or between Socatra and the Maldives, and in the other case between Bombay and Muscat. This, however, has already been encountered and overcome on four several voyages by the Hugh Lindsay to Suez : that the from Bombay vessel encountered a still longer run on these several trips, by going, not to Socatra, but to Aden, a point on the coast of Arabia, near the Straits of Babel Mandeb, being a run of one thousand six hundred and forty-one miles, which she performed in ten clays and nineteen hours. The same trip has since been repeatedly made by other steamers; and, in the present improved state of steam navigation, no insurmountable obstacles are opposed to their passage.







(228) The credit of having afforded the first practical solution of the problem to apply the steam engine to the propulsion of ships, undoubtedly belongs to the people of United States of America. The geographical character of the vast country, not less than the sanguine and enterprising spirit of the nation, contributed to this. A coast of four thousand miles in extent, stretching from the Gulf of St. Lawrence to the embouchures of the Mississippi, indented and serrated in every part with natural harbors and sheltered bays, and fringed with islands forming sounds -capes, and promontories enclosing arms of the sea, in which the waters are free from the roll of the ocean, and take the placid character of lakes, rivers of imposing magnitude, navigable for vessels of the, largest class, for many hundreds and in some instances for many thousands of miles, affording access to the innermost population of an empire, whose area vastly exceeds the whole European continent,-chains of lakes composed of the most extensive bodies of fresh water in the known world, and this extensive continent peopled by races carrying with them the habits and feelings together with much of the &kill and knowledge of the most civilized parts of the globe, endowed also with that inextinguishable spirit of enterprise which ever belongs to an emigrant people, form a combination of circumstances more than sufficient to account for the fact of this nation snatching from England, the parent of the steam engine, the honour of first, bringing into practical operation one of the most important if indeed it be not altogether the most important of the many applications of that machine to the uses of life. The circumstances which rendered these extensive tracts of inland and coast navigation eminently suited to the application of steam power, formed so many obstructions and difficulties to the application of other more ordinary means of locomotion on water. The sheltered bays and sounds which offered a smooth and undisturbed surface to the action of the infant steamer argued the absence of that element which gave effect to the sails and rigging of the wind-propelled ship, and the rapid currents of the gigantic streams formed by the drainage of this great continent, though facilitating access to the coast, rendered the oar powerless in the ascent. (229.) The first great discovery of Watt had scarcely been realized in practice by the construction of the single-acting steam-engine, when the Speculative and enterprising Americans conceived the project of applying it as a moving power in their inland navigation. So early as the year 1783 Fitch and Rumsey made attempts to apply the single-acting engine to the propulsion of vessels, and their failure, is said to have arisen more from the inherent defects of that machine in reference to this application of it, than from any want of ingenuity or mechanical skill on their parts. In 1791, John Stevens of Hoboken commenced his experiments on steam navigation, which were continued for sixteen years; during a part -of this period he was assisted by Livingstone (who was subsequently instrumental in advancing the views of Fulton), and by Roosevelt. These projectors had, at that time also, the assistance and advice of Brunel, since so celebrated for the invention of the block )machinery, and the construction of the Thames Tunnel. Their proceedings were interrupted by the appointment of Livingstone as American Mister at Paris, under the Consular Government. At Paris, Livingstone met Fulton, who had been previously engaged in similar speculations, and being struck with his mechanical skill, And the soundness of his views, joined him in causing a series of experiments to be made, which were accordingly carried on at Plombi6res, and subsequently on a still more extensive scale on the Seine, near Paris. Having by this course of experiments obtained proofs of the efficiency of Fulton's projects, sufficient to satisfy the mind of Livingstone, he agreed to obtain for Fulton the funds necessary to construct a steam boat on a large scale, to be worked upon the Hudson. It was decided, in order to give the project the best chance of success, to obtain the machinery from Bolton and Watt. In 1803, Fulton accordingly made drawings of the engines intended for this first steamer, which were sent to Soho, with an order for their construction. Fulton, rnean while, repaired to America, to superintend the construction of the boat. The delays incidental to these proceedings retarded the completion of the boat and machinery until the year 1807, when all was completed, and the first successful experiment' made at New York. The vessel was placed, for regular work, to ply between' New York and Albany.),, in the beginning of 1808; and, from that time to this present, this river has been the theatre of the most remarkable series of experiments on locomotion on water which has ever been presented in the history of navigation.

(230.) The form and arrangement of this first marine engine was, in many respects, similar to that which is still generally used for marine purposes. The cold water cistern was abandoned, and an increased condensing power obtained by enlarging the condenser. It was usual to make the condenser half the diameter of the cylinder, and half its length, and therefore one eighth of its capacity The condenser, however, was now made of the same diameter as the cylinder, being still half its length; its capacity therefore, instead of being only an eighth, was half of the cylinder; the condensing jet by a pipe passing through the bottom of the vessel. As in the present marine engines, two working beams were provided, one at either side of the cylinder; but in order to provide against the difficulties which might arise in the adaptation of machinery made at Birmingham to a vessel made at New York, beams were constructed in the form of an inverted I, the working arms being twofold, one horizontal and the other vertical, so that the connecting rod might be sea from the crank, either downwards, to the end of the horizontal arm, or horizontally, to the end of the vertical arm. In fact there was a choice, to use either a straight beam, or a bell-crank. The latter was that which was adopted in this instance. The paddle-shaft, driven by the crank, passed across the vessel, and had the paddle-wheels keyed upon it as at present; and in order to equalise the effect of the engine spur wheels were also placed on the paddle-shaft, by which pinions were driven, placed upon an axle, which carried flywheel. The speed attained by this steam boat, when it first began to ply upon the river, did not exceed four miles an hour, but by a series of improvements its rate of motion was soon increased to six miles an hour. in the steam boats subsequently constructed by Fulton a greater speed was attained; but in the latest vessels built by him he did not exceed a speed of nine miles an hour, which be considered to be the greatest that could be advantageously obtained. While Fulton was making his plans, and engaged in the construction of his first boat, Mr. Stevens of Hoboken, already mentioned, was engaged in a like project, and completed a vessel, to be propelled by a steam engine, within a few weeks after the first successful voyage of Fulton. Stevens was likewise completely successful; but the exclusive .privilege of navigating the Hudson by steam having been granted to Fulton by an act of Congress, Stevens was compelled to select another theatre for his operations, and he accordingly sent his steam boat by sea to Philadelphia, to navigate the Delaware, thus securing for himself the honour of having made the first sea voyage by steam. Fulton did not long retain the monopoly of the steam navigation of the Hudson. Fortunately for the progress of steam navigation, the act conferring upon him that privilege was declared unconstitutional; and the navigation of that noble river was thrown open to the spirit and enterprise of American genius. The number of passengers conveyed upon it became enormous beyond all precedent, and inducements of the strongest kind were accordingly held out to the improve-ment of its navigation. The distance between New York and Albany, ascertained by a late survey to be one hundred and twenty-five geographical miles by water had been performed by Fulton boats occasionally in fifteen or sixteen hours, being at the rate of about 'eight miles an hour, including stoppages. It became a great object to increase the speed of this trip, so that it might 4#t all times of the year be performed between sunrises and sunset. Robert L. Stevens, the son of the person of that name already mentioned, immediately after the abolition of Fulton's monopoly, placed on the river a vessel which had been built for the Delaware, which easily performed the' passage in twelve hours, being at the rate of nearly ten and a half geographical miles an hour. By this increase of speed the improved boats.3o entirely monopolised the day work upon the river, that the former steamers were either converted into steam tugs to draw barges laden with goods, or used for night trips between New York- and Albany. In the night trips the saving of one or two hours was immaterial, it being sufficient that the vessel which left the one port at night should reach the other in the morning.

The river Hudson rises near Lake Champlain, the easternmost of the great chain of lakes or inland seas which extend from east to west across the northern boundary of the United States. The river follows nearly a straight course southwards for two hundred and fifty miles, and empties itself into the sea at New York. The influence of the tide is felt as far as Albany, above which the stream begins to contract. Although this river in magnitude and extent is by no means equal to several others which intersect the States, it is nevertheless rendered an object of great interest by reason of the importance and extent of its trade. The produce of the state of New York and that of the banks of the great Lakes Ontario and Erie are transported by it to the capital; and one of the most extensive and populous districts of the United States is supplied with the necessary imports by its waters. A large fleet of vessels is constantly engaged in its navigation; nor is the tardy but picturesque sailing vessel as yet excluded by the more rapid steamers. The current of the Hudson is said to average nearly three miles an hour; but as the ebb and flow of the tide are felt as far as Albany, the passage of the steamers between that place and New York may be regarded as equally affected by currents in both directions, or nearly so. The passage therefore, whether in ascending or descending the river, is made nearly in the same time. (231.) The prevalence of smooth water navigation, whether on the surface of rivers or in sheltered bays and sounds, has invested the problem of steam navigation in America with conditions so entirely distinct and different from those under which the same problem presents itself to the European engineer, that any comparison of the performance of vessels, Whether with regard to speed or the absorption of power in the two cases, must be utterly fallacious. In Europe a steamer is almost invariably a vessel designed to encounter tile agitated surface of an open sea, and is accordingly constructed upon principles of suitable strength and stability. It is likewise supplied with rigging and with sails, to be used in aid of the mechanical power, and manned and commanded by experienced seamen ; in fact, it is a combination of a nautical and mechanical structure. In America, on the other hand, with the exception of the vessels which navigate the great northern lakes, the steamers are structures exclusively mechanical, being designed for smooth water. They require no other strength or stability than that which is sufficient to enable them to float and to bear a progressive motion through the water. Their mould is conceived with an exclusive view to speed; they are therefore slender and weak in their build, of great length in proportion to their width, and having a very small draugbt of water. In fact, they approach in their form to that of a Thames wherry on a very large scale. The position and form of the machinery is likewise affected by these conditions. Without the necessity of being protected from a rough sea, it is placed on the deck in an elevated position. The cylinders of large diameter and short stroke invariably used in Europe are unknown in America, and the proportions are reversed, a small diameter and stroke of great length being invariably adopted. It is rarely that two engines are used. A single engine, placed in the centre of the deck, with a cylinder from forty to sixty inches' diameter, and from eight to ten foot stroke, drives paddle-wheels from twenty-one to twenty-five feet in diameter, producing from twenty-five to thirty revolutions per minutes The great magnitude of the paddle-wheels and the velocity impacted to them enable them to perform the office of fly-wheels, and to carry the engine round its centres, not however without a perceptible inequality of motion, which gives to the American steamer an effect like that of a row boat advancing by starts with each stroke of the piston, The length of stroke adopted in these engines enables them to apply with great effect the expansive principle, which is almost universally used, the steam being generally cut off at half stroke.

The steamers which navigate the Hudson are vessels of considerable magnitude, splendidly fitted up for the accommodation of passengers they vary from one hundred and eighty to two Hundred and forty feet in length, and from twenty to thirty feet in width of beam In the following table is given the particulars of nine steamers plying on this river, taken from


    NAME          Length     Breadth       Draft Drain  Length      Depth      Num.       Drain

                  of Deck    of Beam      of Water      of Wheel     of Paddles            of Paddles      of Engs. of Cyl.
Ft.               Ft.        Ft.    Ft.    Ft.    Ft.    Ft.          Ft.

    Clinton       230        28     5’5    21     13’7   36           1          65

    Champlain     180        27     5’5    22     15     34           2         44

    Erie          180        27     5’5   22     15     34           2          44

    N. America    200        30     5      21     13     30           2          44’5

    Independence 148        26     /      /      /     /           1         44

    Albany        212        26     /      24’5 14     30           1          65

    Swallow       233        22’5   3’75   24     11     30           1          46M

    Rochester     200        25     3’75   23’5   10     24           1          43

    Utica         200        21     3’5    22     9’5    24           1          39

The hulls of these boats are formed with a perfectly flat bottom and perpendicular sides, rounded at the angles, as represented in fig. 135. At the bow, or cutwater, they are  made very sharp, and the deck projects to a great distance over the sides. The weight of the machinery is distributed over an extensive surface of the bottom of this feeble structure, by means of a framework of substantial carpentry to which it is attached. At the height of from four to six feet above the water-line is placed the deck, which is a platform, having the shape of a very elongated ellipse.

Fig. 135

The extremities of its longer axis are supported by the sternpost and tile cutwater, and its sides expand in gentle curves on either hand to a considerable distance beyond the limits of the hull; those parts of the deck thus overhanging the water are - called the wheel guards. Beneath the first deck is the saloon, or dining-room, which also, as is usual in European ' steamers, forms the gentlemen's sleeping-room. It usually extends from end to end of the vessel. The middle of the first deck is occupied by the engine, boilers, furnaces, and chimneys, of which latter there are generally two. , Between tile chimneys and the stern, above the first deck, is constructed the ladies cabin, which is covered by the second deck, called the promenade deck. The great length of these boats and, the elevation of tile ethnic.,, render it impossible for a steersman at the stern to see ahead, and they are, consequently, steered front the bow: the wheel placed there communicating with the hull at the stern, by chains or rods carried along the sides of the boat. Until a recent period, the wheel was connected with the stern by ropes, but some fatal accidents, produced by fire, in which these-- ropes were burnt, and the steersman lost all power to guide the vessel, caused metal rods or claims to be substituted. (232.) The paddle-wheels universally used in American steam-boats are formed, as if by the combination of two or more common paddle-wheels, placed one outside the other, on the same axle, but so that the paddle boards of each may have an intermediate position between those of the adjacent one, as represented in fig.136

Fig. 136


The spokes, which are bolted to cast-iron flanges, are of wood. These flanges, to which they are so bolted, are keyed upon the paddle shaft. The outer extremities of the spokes are attached to circular bands of iron, surrounding the wheel; and the paddle boards, which are formed of hard wood, are bolted to the spokes. The wheels thus constructed, sometimes consist of three, and not infrequently four, independent circles of paddle boards, placed one beside the other, and so adjusted in their position, that the boards of no two divisions shall correspond.

The great magnitude of the paddle-wheels, and the circumstance of the navigation being carried on, for the most part, in smooth water, have rendered unnecessary, in America, the adoption of any of those expedients for neutralising the effects of the oblique action of the paddles, which have been tried, but hitherto wit], so little success, in Europe.

Sea going steamers arc not numerous the chief of them being those which ply between New York and Providence, and between New York and Charleston. These vessels, however, do not reliable the sea-going steamers of' Europe as closely is ,night be expected; and to the latter, the sea-going steamers of America can hardly be regarded as safe means of transport.

The Narragement, the finest of these vessels, is built of oak, strengthened by diagonal straps or ties of iron, by which her timbers are connected; site is driven by a condensing engine, and has two boilers, exposing about three thousand square feet of surface to the fire. The steamer is maintained at a pressure of twenty to twenty-five tbs. per square inch: the cylinder is Horizontal. The cabins of these sea-boats are of great magnitude, and offer excellent accommodation for containing generally four hundred berths.In the Massachusetts the chief cabin is one hundred and sixty feet long, twenty-two feet wide, and twelve feet in length, its vast extent being uninterrupted by pillars or any other obstruction. ,I have dined," says Stevenson, with one hundred seventy persons five ion this cabin not withstanding this numerous assembly, the tables which were arranged in two parallel rows. There are on hundred and twelve fixed berths can be erected in the middle of the floor: besides these there are sixty fixed berths in the ladies' cabin and several temporary sleep ing places can be erected in it also. The cabin of the Massachusetts is by no means the largest in the United States. Some steamers have cabins upwards of one hundred and seventy-five feet in length. Those large saloons are lighted by Argaild lamps, suspended from the ceiling, and their appearance, when brilliantly lighted up and filled with company, is very remarkable. The passengers generally exchange themselves in parties at the numerous small tables into which the large tables are converted after dinner, and engage in different amusements. The scene resembles much more the coffee-room of some great hotel than the cabin of a floating vessel." (234.) Nothing has excited more surprise among engineers and others interested in steam navigation in Europe, than the statements which have been so generally and so confidently made of the speed attained by American steamers. This astonishment is due to several causes, the chief of which is the omission of all notice of the great difference between the structure and operation of the American steamers and the nature of the navigation in which they are engaged, compared with the structure and operation of, and the navigation in which European steamers are employed: as well might the performance of a Thames wherry, or one of the fly-boats on the northern canals, be compared with that of the Great Western, or the British Queen. The statements alluded to all have reference to steamers navigating the Hudson between New York and Albany, the form and structure of which we have already described; and doubtless the greatest speed ever attained on the surface of water has been exhibited in the passages of these vessels. Mr. Stevenson states, that exclusive of the time lost in stoppages, the voyage between New York and Albany is usually made in ten hours. Dr. Renwick, however, who has probably more extensive opportunities of observation, states, that the average time, exclusive of stoppages, is ten hours and a half. The distance being 125.18 geographical miles, the average rate would therefore be 11 9/10 miles per hour, If it be observed that the average rate of some of the best sea-going steamers in Europe obtained from experiments and observations made by myself, more than three years ago, showed a rate of steaming little less than ten geographical miles per hour, and that since that time considerable improvements in steam navigation have been made, and further, that these performances were made under exposure to all the disadvantages of an open sea, the difference between them and the performance of the American river steamers will cease to create astonishment. Dr. Renwick states that be made, in a boat called the 46 New Philadelphia," one of the most remarkable passages ever performed. He left New York at five in ' the afternoon, with the first of the flood, and landed at Catskill, distant 95-8 geographical miles from New York, at a quarter before twelve. Passengers were landed and taken in at seven intermediate points: the rate, including stoppages, was therefore 14-2 miles per hour; and if half all hour be allowed for stoppages, tile actual average rate of motion would be fifteen miles and three quarters all hour. As the current, which in this case was with the course of the vessel, did not exceed three miles and a half an hour, the absolute velocity through the water would have been somewhat under twelve miles an hour. This speed is nearly the same as the speed obtained from taking the average time of the voyages between New York and Albany at ten hours and a half ; it would therefore appear that the great speed attained in this trip must have been chiefly, if not altogether, owing to the effect of the current. (235.) The steamers which navigate the great northern lakes differ so little in their construction and appearance from the European steamboats, that it will not be necessary here to devote any considerable space . to an account of them. These vessels were introduced oil the lakes at about the same time that steamers were first introduced oil the Clyde. These steamers are strongly built vessels, supplied with sails and rigging, and propelled by powerful engines. The largest in 1837, when Mr. Stevenson visited the States, was the James Madison. This vessel was one hundred and eighty one feet in length on the deck, thirty feet in breadth of beam, and twelve feet six inches in depth of hold: her draught of water was ten feet, and her measured capacity seven hundred tons. She plyed between Buffalo on Lake Brie and Chicago Lake Michigan, a distance of nine hundred and fifty miles The severe storms and formidable sea encountered on the lakes render necessary for tile navigation, vessels in all respects as strong and powerful us those which navigate the open ocean. (M.) By for the most remarkable and important of all the American rivers at the Mississippi and distributors. That part of the American continent which extends from the southern shores of the great northern lakes t o tile northern shores of the Gulf of Mexico, is watered by these great streams. The main stream of the Mississippi has its fountains in the tract of country lying north of the Illinois and east of Lake Michigan, in latitude forty-three degrees. At about latitude thirty nine degrees, a little north of St. Louis, it receives the waters of the Missouri, and further south, at the latitude of thirty seven degrees, the Ohio flows into it, after traversing five degrees of longitude and four of latitude, and winding its way from the Alleghany ranged through several of the states, and forming a navigable communication with numerous important towns of the Union, among which may be mentioned Pittsburgh, Cincinnati, Frankfort, Lexington, and Louisville. The. Main stream of the Mississippi, after receiving the waters of the Arkansas, and numerous other minor tributaries, flows into the Gulf of Mexico by four months. The main stream of the Mississippi, independently of its tributaries, forms an unbroken course of inland navigation file r a distance of nearly two thousand three hundred miles. Its width, through a distance of one thousand one hundred miles from its mouth, is not less than half a mile, and its average depth a hundred feet. The Ohio, its chief eastern tributary, flowing into it at a distance of about a thousand miles, from its mouth, traverses also about the same extent of country, and is navigable throughout the whole of that extent. This river also has several navigable tributaries of considerable extent, among which May be mentioned the Muskingum, navigable for one hundred and twenty miles ;'the Miami, navigable for seventy five miles; the Scioto, navigable for one hundred and twenty miles; the Tennessee, navigable for two hundred and fifty miles; the Cumberland, 'navigable for four hundred end forty miles; the Kentucky, navigable for one hundred and thirty miles; and the Green River, navigable for one hundred and fifty miles. The total length of the Ohio and its tributaries estimated at above seven thousand miles. (237.) Steam-boats were introduced on the Mississippi about the year 1812, the period of their first introduction in Europe; and their increase has been rapid beyond all precedent. In the year 1831 there were one hundred and ninety, eight steamers plying on its waters; and the number in 1837 amounted to nearly four hundred. These vessels are built chiefly on the banks of the Ohio, at the towns of Pittsburgh and Cincinnati, at distances of about two thousand miles from the mouth of the river they are intended to navigate. (238.) These steamers, which are decidedly inferior to those which navigate the eastern water, are generally of a, heavy build, fitted to carry goods as we as passengers,. and vary from one hundred to seven hundred tons berths. Their draught of water is also greater than that of the eastern river steamer varying from sixty eight feet. The hull about five feet from the water line, is covered with a deck, under which is the hold, in which the heavy part of the is stowed. About the, middle of this deck the engines are placed, the boilers and furnaces occupying a t; pace nearer to the bow, near which deck chimneys are placed. The fire, doors of the furnaces are presented towards the bow, and exposed so as to increase the draught. That part of the first deck which extends from the machinery to the stern is the place allotted to the crew and the deck passengers, and is described as being filthy and inconvenient in the extreme. second deck is constructed, -which extends from the chimneys near the bow to the stern of the vessel. On this is formed the great cabin or saloon, which extends from the chimney* to within about thirty feet of the stern, where it is divided by a horizontal from the ladies ladies' cabin, which occupies the remaining space. These principal cabins are surrounded by a gallery about three feet in width, from which, at convenient places, an ascent is supplied by stairs to the highest deck, called the hurricane or promenade deck. (239.) The engines by which these boats are propelled are totally different from the machinery already described as used in the eastern steamers. They are invariably non-condensing engines, worked by steam of extremely high pressure; 'the boilers are therefore tubular, and the cylinders small in diameter, but generally having a long stroke. The pressure of steam used in these machines is such as is never used in European engines, even when worked on railways. A pressure of one hundred pounds per inch is here considered extremely moderate. The captain of one of these -boats, plying between Pittsburgh and St. Louis, told Mr. Stevenson that 11 under ordinary circumstances his safety valves were loaded with a pressure equal to one hundred and forty-eight pounds per square inch, but that the steam was occasionally raised as high as one hundred and fifty pounds to enable the vessel to pass parts of the river in which there is a strong current ;'! and he added, by way of consolation, that 01 this pressure was never exceeded except on extraordinary occasions I" The dimensions and power of the Mississippi steamers may be collected from those of the St. Louis, a, boat which was plying on that river in 1837. That vessel measured two hundred and fifty feet on deck, and had twenty-eight feet breadth of beam. Her draught of water was eight feet, and her measured capacity one thousand tons. She was prepared by two engines with thirty-inch cylinders, and ten feet stroke; the safety valve being loaded at one hundred pounds per square inch. The paddle wheels of these vessels are attached to the paddle shaft, in such a manner as to be thrown into and out of gear, at discretion, by the engineer, so that the paddle shaft may revolve without driving the wheels: by the expedient the power of the engine is used to feed the boilers while the vessel stops at the several stations. The vessel is therefore stopped, not, as is usually the case, by stopping the engines, but by throwing the wheels out of connection with the paddle shaft. The engines continue to work, but their power is expended in forcing water into the boiler. By this expedient the activity of the engines may, within practical limits, be varied with the resistance the vessel has to encounter. In working against 4 strong current, the feed may be cut off from the boilers, and the production of steam, and consequently the power of the engines, thereby stimulated, while suspension of the feed may be compensated at the

next station. The stoppages to take in goods and passengers, and for relays of fuel, are frequent. 91 The liberty which they take with their vessels on these occasions," says Mr. Stevenson, 41 is somewhat amusing: I had a good example of this on board a large vessel, called the Ontario. She was steered close in shore amongst stones and stumps of trees, where she lay for some hours to take in goods: the additional weight increased her draught of water, and caused her to heel a good deal; and when her engines were put in motion, she actually crawled into the deep water on her paddle wheels: the steam had been got up to an enormous pressure to enable her to get off, and the volume of steam discharged from the escarpment pipe at every half stroke of the piston made a sound almost like the discharge of fire-arms, while every timber in the vessel seemed to tremble, and the whole structure actually groaned under the shocks." Besides the steamers used for the navigation of the Mississippi, innumerable steam tugs are constantly employed for towing vessels between the port of New Orleans and the open sea of the Gulf of Mexico. Before the invention of steam navigation, this southern capital of the United States laboured under the disadvantage of possessing almost the only bad and inconvenient harbour in the vast range of coast by which the country is bounded. New Orleans lies at a distance of about one hundred miles from the Gulf of Mexico. The force of the stream, the frequency of shoals, and the winding course of the channel rendered it scarcely possible for a sailing vessel to pass between the port and the sea with the same wind. The anchorage was every where bad, and great difficulty and risk attended the mooring of large vessels to the banks. The steam engine has, however, overcome all these difficulties, and rendered the most objectionable harbour of the Union a safe and good seaport, perfectly easy of approach and of egress at all times ; a small steam tug will take in tow several large ships and carry them with safety and expedition to the offing, where it will dismiss them on their voyage, and take back vessels which may have arrived.


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Rev. January 2011