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along against each side of the vessel, 'zontally (the plate being nearly of equal the edge of which is fitted up against strength in both directions), whilst it will the ribs and riveted on to the flat angle require, in a timber-built ship, fir planks iron beams. This continuous plate is of about 4 inches thick, to be of equal made of the ordinary boiler plates, united sectional strength, and which will be at the end with a jointing fillet" single making no allowance or deduction for riveted” to each, and over it are laid the the butt joints. In this comparison of deck planks, to which they are bolted ; it strength, I have entirely disregarded the being therefore firmly secured between frame timbers in timber-built ships, and the beams and planking, cannot fail to ribs in those of iron, and shall only conaid very materially in resisting any sud sider each as forming the frame work. den and partial resistance externally, and A horizontal seam of rivets as above, if to maintain the original form.

100 feet in length, will bear a strain of The upper, or main deck, is planked 9450 tons, whilst the strength of a plank longitudinally 3 inches thick in the mid- joint, independent of the trenails (which dle, 6 inches near the sides, from which places both under the same condition), there is a mass of timber forming the is nothing. “water ways" increasing from 6 inches This absence of union and strength in to about 2 feet in depth against the out the planking joints of timber ships is the side plating, forming a curve surface primary cause of their weakness, and but against the ship's side above and below, for the friction and compression caused to admit of which, the iron beams are by the caulking, in horizontal planking, bent down at the ends. The planking

would be much more so. To this cir of the first saloon deck consists also of cumstance, chiefly, may be attributed the longitudinally laid planks 6 inches wide, hogging" or dropping of the extremi4 inches thick, with “water ways" 10 ties of a ship by the 'unsupported overinches thick at the sides; and, as it lies hanging ends, on its being launched and on the before-mentioned horizontal plates, taking its immersed support on the water, the projection is all above the surface of which I have understood has occasionally the deck. The planking of the third amounted in ships of war to from 8 to 10 deck runs across the ship, with 6 x 4 inch inches. water ways, as in that immediately above. The diagonal planking of Seppings is

Mr. Grantham thinks that cabins, admirably calculated to make a much decks, masts, &c., will ultimately be made better use of materials than the former of iron. To decks made of iron plates I plan, for by the planks crossing each think the sailor would have a very stand other, and forming an infinite number of ing objection, and iron fittings for cabins triangles with the apex downwards, and would not be very consistent with the re the upper parts being united by strong quirements of refined society. Mr. G. tension stringers-probably the strongest has entitled himself to great credit for wooden fabric possible is obtained. This having given the subject of iron ship observation may raise the question (much building a most interesting and masterly easier asked than answered), why it is investigation.

that the diagonal plan was not in use Mr. Fairburn says, that plate iron will much earlier, since every boy who bear a strain of 22 tons, in the direction rides on a five-barred gate knows that of its fibre, per square inch, and still without the diagonal his horse's head more across the fibre; while the Franklin would drop ? The very best combination Institute make it rather less, as any one of wood, or of wood and iron, that can would from common experience expect, be devised, appears, however, very far but this does not materially affect the below the strength which may be obpresent inquiry. He also says, that dou tained by plates of iron in forming the ble riveting is stronger than single, in hull of a ship. the proportion of 70 to 56 ; or, the The greater capacity of an iron-built strength of plate being 100 single rivet ship will also be a matter of consider. ing, will be 56 and double 70 respect. able importance; as, from the absence of ively. A plate 2 feet wide x thick will floor and frame timbers, kelsons, linings, bear a strain in the direction of its length deck-beams, and knees, the stowage will of 337 tons, and at the joints, if single ri. be materially increased over a timber veted, 189 tons, both vertically and hori- ship, though the external dimensions be

the same, and which, in the Great Bri average tuickness would be reduced to tain, I imagine would not be less than -inch ; besides, corrosion will not go on 1000 cubic yards.

uniform!), some parts will be nibbed As the form may easily be maintained quite through, whilst others will be much by internal framing, bracing, and truss less affected. This is a matter requiring ing, what is there to limit the size of more research. ships, except the draft of water in ports, But of all the patent plans for the mercantile convenience wharfs, quays, “ galvanization of iron" to prevent oxy&c. ? I do not see any reason connected dation, brought forth a few years since, with the construction, or in an engineer I do not know of one that is in use. ing point of view, why the Great Britain The first iron steamer, as appears by Mr. may not hereafter be considered an or Grantham, was the Aaron Manby, condinary sized vessel, instead of being "out structed by the Horsley Company in rageously large" as she is now called, 1821, and I am pleased to see that she is

There may be more advantages ob still in use, from the circumstance of tained by large steam vessels than at pre having been present at Horsley when the sent occur to me, but I will mention

parts were shipped into the canal boat. what appear some of the most prominent. My recollection of the thickness of the The greater the length of a vessel the plates is imperfect, but I have an impresgreater will be the broad-side resistance sion that they were not more than ths, against the water, and consequently less if even so much, and that all the joints "lee way" will ensue, and less will be were flush. Mr. Grantham thinks that the disturbance by waves from a straight “plates may probably be yet required of line, and consequently, the velocity will much greater strength than fths of an be less detracted by the water impinging inch thick.” Surely no peaceful mariagainst the rudder. Adverse storms and time occupation can require it, and as heavy seas will be of less consequence, good citizens of the commonwealth we and such as would founder moderate size ought no longer to indulge in forming ships may be regarded in a large one as plans to defeat cannon balls, for which insignificant. The displacement, and only, or " hammering on rocks” can therefore capacity of the vessel increasing such a thickness be required. If larger as the cube, whilst the section of resistance vessels than the Great Britain are built, increases as the square of dimensions, it and more strength be considered necesfollows that a less proportion of power to sary, the most advantageous disposition tonnage will be sufficient. Large en of it would be in ribs and bones and not gines and large fires will work more ad in the skin. vantageously than small ones. The fric

The Machinery. tion of parts generally will increase as their diameters, whilst the areas under The boiler, as will be seen by the acpressure of useful effect will increase as companying sections, presents a great the square of the diameters, and twisting quantity of surface to the action of the or torsion as the cube of the diameters. fire and heated air, and appears amply Radiation of heat also from the surface of strong for condensing engines. boilers, steam-pipes and cylinders will In wooden-built steamers there is an follow the same law.

absolute necessity to guard against the What the durability of iron plates in possibility of the timbers taking fire; and a sea vessel may be, does not appear to

for this reason the boilers have been be very clearly established. Mr. Mallet constructed with water spread all over says, that a half-inch plate will last 100 the surface of the bottoms below the fires; years exposed to sea water, but it must but as the same necessity does not exist be considered that the inside of the bot in iron vessels, it occurs to me that the tom of a ship will be exposed to the entire quantity of boiler plates and water bilge-water, and therefore the period will below the line of the fire-bars, but for be reduced to 50 years. If in 50 years the deposition of salt, is useless and una half-inch plate be half worn away on necessary. It is not to be supposed that the outside by corrosion, and the other any portion of the current of flame will half be reduced to an oxide on the inside, dip down at the back of the bridge and it is perfectly clear that it could not form impart heat to the sides, even much less part of a ship, even 25 years, when the will it touch the bottom, and then creep

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up against the back before it escapes to flue plates. I believe in almost all cases the upper flue; the cause of the air of boilers with large flues, by far the being drawn into the fire, being the in greatest quantity of heat is imparted to serior specific gravity of that contained the water by the roof of the fire-place, and in the chimney, caused by its expansion Alues, and my present impression is, that by heat; and as the drawing power of were all that mass of water, amounting to the chimney extends to the fire, the cen probably not less than 2,500 cubic feet, tre of the current of heat will take the or about 70 tons weight, and nearly 40 shortest course (except, that some trilling tons of boiler work removed, and the deviation will take place in the curves bottoms of the flues made good in anoof the currents at the bends of the flues), ther way, the heating power and effect of and all Alue space to which the current the boilers would be still nearly equal. does not extend, will be occupied by the If this view of the question be correct, heavy carbonaceous gases in a quiescent there is then also a sacrifice of space unstate, possessing a very small power of der the boiler of about 20 feet long, by transmitting heat from the current to the the width of the ship, and at least 6 feet

cover.

high in the centre, which might have depth 7 to 8 inches, to be packed behind. been available for spare sets of engine The nuts for holding down screws for work (if it be intended to carry such,) the packing ring are turned cylindrical, or other heavy stores, which would and inserted into holes of 21 inches dia. compensate for the centre of gravity of meter, drilled in the top of the piston. the boiler being raised, should that be The holes to be expanded by heat, and considered an object.

the nuts inserted cold, so as to be held It will probably be said, that this boiler in by friction, and probably farther sespace is necessary for the reception and cured by a tap screw, but this I did not subsidence of the salt, and that less notice. How much better this plan may would not do. But it would still appear be than either mortice or dovetailed nuts, that, were the whole of the bottom raised I am not prepared to say. up to about a level with the top of the The piston rod is forged with an eye bridges, some advantage in heating would at the top for the connecting pin, and the be obtained, a considerable space be gain- lower end in the piston is parallel, or ed for other purposes, and ample room be nearly so. The guide frames for the top left for the subsidence of the heavy saline of the piston rod are fixed to the cylinder water, combined too with an equally effective arrangement for “blowing off.” The shells of the piston valves are

brass cylinders with steam openings, as The Engines.

shown by the sections, having a “twist," I find it is still believed by some per- apparently for the purpose of causing the sons that the engines are to be constructed wear to be more uniform. On the outon the “trunk principle” of the late Mr. side of this brass casing there is an anHumphreys; but such is not the case here nular chamber leading to the cylinders. adopted, but rather approaching the pa The piston valves are also each furnished tent plan of Sir Mark Brunel, at least in with a cast iron expanding ring, as bethe position of the cylinders, except that fore described, for the cylinders. (Had instead of the cylinders making a right my old friend, the late talented Arthur angle, or 90° with each other, they stand Woolf, adopted an arrangement of this at an angle of 60°, or thereabouts. From kind in his " steam plug" to his small the dimensions and particulars already cylinder, he would have been more sucgiven, your readers will have so far be cessful.) This form of valve, side pipes, come acquainted with this branch of the &c., makes a convenient arrangement, subject as to render it superfluous to do but still leaves the question open as to more than advert to such additional de whether it is better, if as good, for large tails as appear to possess novelty, and engines, as the lantern valve of another may therefore be interesting. It will be scientific gentleman (of whose kindness observed, that the foundation plate has a and urbanity I have a very grateful conical depression of about 12 inches, recollection,) the late Jonathan Horninto which the piston dips; this depres- blower. sion fits into the bend of the ship, and is These valve pistons are to be worked therefore taken advantage of in depress by eccentrics in the usual way; but I ing both faces of the piston, and also understand the "6 reversing" is

to be dishing the cylinder cover to about eight effected by an 8 feet spur-wheel being inches at the centre, thereby affording attached to the eccentric, with a pinion the connecting rod to be that much to slide into gear with the wheel, on the longer. The piston is cast with its top spindle of which pinion there is to be a and bottom face, arms, and outer ring, in spoke-wheel, similar to a tiller-wheel, one piece ; and for the purpose of fitting and the eccentric is to be driven by the in the keys to fasten the rod there are main shaft through the intervention of a two holes, into one of the spaces between “ sliding clutch." the arms, through which the fitting and The expansion valves are similar to the fastening is performed, and which holes sliding ventilators used for admitting ho are then stopped by circular plates, with air into buildings, and there being four valve mitre edges, and made fast. The openings in the length of the valve, the rubbing, or "metallic" surface of the orifice opened for the admission of steam piston, is one ring of cast iron, cut open to the valve pistons will be four times the at one point, with a half-lapped joint, length of stroke of the valve, whatever

hat may happen to be. Throttle valve The condensers being of more than of the usual kind. The air pumps (brass the usual proportions, may be expected lined) are to stand partly in the conden to make a more uniform vacuum than is sers, with the foot valves at their lower generally found to exist; and to produce ends. Air pump rods (iron, brass cased) a better test card, though perhaps not have also an eye at their upper end for higher, or even so high as the “patent the connecting pin. The connecting best” of 36 inches. joint of the air pump is kept in its right I saw none of the endless schemes of line by parallel motion rods, by one set which so much was said yesterday, and of which are moved the boiler and bilge so little will be known to-morrow. Still, pumps. The connecting rods of two if schemes be not introduced, we cancylinders and of one air pump are at not reap the benefits. For instance, the tached to the same crank pin, and the patent condenser, with its 14 miles of bearings on the crank pin are turned 1-inch pipe, and 40,000 joints, saving 15 spherical.

per cent.---patent boilers, 25 per cent.The most extraordinary part of the patent fuel, 30 per cent.-smoke burners, whole machinery, and more particularly 35-rotary engines, 40-patent engines deserving notice than any other, is the with slots in the sides and trunks in the wrought iron main sliaft, made at the middle, besides all that never-ceasing Mersey Iron Works, Liverpool. In the variety of patent paddles and patent prorough it appeared quite sound, and pellers, (one screw that is to be exceptnearly as well hammered as an anchor. ed,) calling into use so many high-soundI have also seen it since it was turned, ing names, and flourishing more geo. and partly bored, but did not under metry than Euclid ever dreamed of. stand there were any serious defects in Think of the boundless wealth which it, though it was said to be “ hollow" must accrue to that man who would be in places.

bold enough to amalgamate all these eleThe model exhibited to the public has ments into one vast machine, that would its cranks in opposite directions from the require so much less than nothing to centre of the shaft, and which the exhi keep it going, and have " oceans' of bitor said was correct; I have therefore

power to spare ! drawn them so, although it is probable a Here would be a “mammoth” indeed! better position will be found. It also I will not prolong this paper by disexhibited a plain strap driving-wheel on cussing the merits of the screw as a prothe main shaft, with a pulley below on peller, or trouble you with an opinion; the screw spindle, which, it was said, is besides, neither you nor your readers to make 80 revolutions per minute; but it want it, for you have them of all shapes appears that the method intended to com and sizes, and to suit every purpose and municate the power from the engines to fancy. the screw, as also the construction of the There are decided disadvantages insescrew, is not yet decided on, although it parable from the use of the paddle-wheel was said to be “all sellled.

system, such as the great weight of upper The whole of the work appears ex works, shafts and engine framing, wheels tremely well executed, the details to have and framing, paddle-cases, and a variety been considered with great care and judg of ponderable matter, all tending to keep ment, and the proportions, with some the centre of gravity in an elevated posiexceptions, are well maintained. When tion; greater exposed front surface to finished, and set to work, I have no doubt head winds, or side surface with wind on they will prove good engines.

the beam, and with the lec paddle imIn all combinations of machinery, there mersed to a great depth, and the other are reasons for preferring particular ar frequently whirling in the air ; loss of rangements; and should the screw pro steam power, arising from the obliquity peller prove as effective as has been spoken of paddles in entering and quitting the of, the reasons for this arrangement of water, forcing some below and throwing machinery will be suflicient to entitle it much above the surface; from the great to public approbation ; but, otherwise, I believe it will be admitted, that any po

immersion of paddle-wheels on leaving

port with a full cargo, and too little when sition for a large steam cylinder, oui of sight; strain and tremor from machinery the verticul, makes but a second-raie running through the upper part of the affair.

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