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tions or ordinates are placed at the rabbets of the the multiplication by the fraction will be neces first have their projections on a plane perpendicular stem and post, as before explained ; and the dis- sary.

to the load water line, and not their true areas, tance between then, measured on the middle line Let us assume, however, that we have obtained but as before the true displacement will be ob. of the half-breadth plan, is divided into a number the true areas of the horizontal sections, and let tained when these are put into the rule,"and the of equal portions suitable for the application of them be respectively represented by 41, A2, A3, common interval taken as measured along the the rules given for obtaining curvilinear areas, 44, 4.1, A3, and 434.

horizontal sections. and at the points of division lines are drawn per To obtain the displacement from these we have

With these observations, we shall leave the pendicular to the middle line. These lines repre- only to multiply them respectively by 2, 6, 6, 3, student to work out the example for himself

, as sent transverse sections perpendicular to the upper 3, 3, and 1, in accordance with the third rule no difficulty can present itself respecting that poredge of the rabbet of the keel, and in Fig. 19 are for finding a curvilinear area, and their sum mul. tion of the displacement which is inclosed by the represented by the vertical sections 1, 14, 2, &c. tiplied by <ths of the perpendicular distance be- extreme sections; the work is precisely the same as The ordinates are then measured off from the

tween the sections, will give the displacement. in our former example. half-breadth plan, and inserted in the table, as Now, the perpendicular distance between any two

The small portions of the displacement situated already described in our former example, and/the sections is equal to the distance between them, outside of the extreme sections are found by the calculations proceedede with as though the trans, measured on a vertical section, multiplied by the ordinary rules of mensuration, as also are their verse sections were perpendicular to the load

centres of gravity, and the necessary corrections fraction : it is obvious, therefore, that if we water sections.

ī

are made in the results before obtained. In our present example, the distance between make use of the projections of the areas of the 5! W.L. contains 167 cubic feet, and its centre of

In the present example the portion below the extreme ,vertical sections measured on the horizontal sections (which are the true areas mul- gravity, situated at b, Fig. 19, is 120 feet from middle line is divided into 18 equal portions, each being 9:4 feet; and for greater accuracy, the two tiplied by the fraction and take the distances section 1, and 12-5 feet from the L. W. L. extreme intervals are again divided into two equal | between the horizontal sections, as measured on a

The contents of the rudder and stern posts portions respectively, as is shown in the Fig. 19.

abaft the section 19 are 65 cubic feet, and the vertical section, we shall obtain the correct disIn placing the horizontal sections they are so

centre of gravity situated at c, Fig. 19, is 180 feet placement. arranged that the third rule for approximating

abaft section 1, and 6.25 feet below L. W. L. the curvilinear areas may be applied. There are

To obtain the displacement by transverse sec

The portion between the stem and the extreme at the upper portion of the displacement four tions, the rationale of the operations will be sections, which must be subtracted, contains 22-8 equidistant sections, and at the lower portion between the horizontal sections is measured along Fig. 19, is 2-5 feet abaft section 1, and 9-5 feet

readily made out. For, since the common interval cubic feet, and its centre of gravity, situated at a, four other equidistant sections.

The common

the transverse sections in the sheer plan, when the below L. W. L. distance between the sections L. W. L. and

ordinates for any section are put into the rule, and 2 W. L.; 2 W. L. and 3 W. L.; 3 W. L. and

The positive portions amount to 167 + 65, or 4 W. L.,' is 2.65 feet, measured on the sections the sum multiplied by the proper fraction of the 232 cubic feet. The negative portion is 22-8 ;

common interval, the result will be the true area drawn perpendicular to the rabbet of the keel, and

the total positive appendage is therefore 209-2

And since the common interval cubic feet, which must be added to 28198-2757, the common

distance between the sections of that section. 4 W. L. and 4} W. L; 4! W. L. and 5 W. L.; dicular distance between any two consecutive ones ; sections, to obtain the total displacement. In

between the transverse sections is the perpen the displacement situated between the extrema 2.65 5 W. L. and 5! W. L. is feet, measured on when their areas are put into the rule, and the forming the scale of displacement, the proper

sum multiplied by the usual fraction of the com-
the same sections.
Performing the calculations in the same man-

mon interval
, the result
will evidently be the dis- appendages must also be taken into the calcu-

lations,
placement.
ner as described in the former example, we obtain

Again, in obtaining the centre of buoyancy in first the areas of the projections of the several

Another explanation may be given of the our former example, there were no appendages to horizontal sections; and before being multiplied the extreme sections from the projections of the of buoyancy corresponding to the portion inclosed

manner of finding the displacement inclosed by the displacement. In the present case, the centre by $rd of the common interval they are to be found outside of the planking, as delineated on the by the extreme sections is found as in that ex: in the first horizontal column below the ordinates; they are 32:75, 93.75, 194:75, 297-5, 452:8, 550-95, building draught. Taking, as before, the extreme ample, and it then remains to find the effect of and 621-4. Suppose we have multiplied these transverse sections at the outside of the rabbet of the appendages upon its position in a vertical and results respectively by one-third of the common

the stem and stern-post at the load water line, also in a horizontal direction. This may be readily interval, and so obtained the areas of the projec. L. W. L. in the sheer plan, and then divided into gravity proved in our last article, page 215.

let the distance between them be measured on the done by means of the property of the centre of tions of the several horizontal sections, these the same number of equal parts as was the dis. Assume that the axes o x, o y both pass through the areas will be equal to the true areas of the respec

tance between them on the iniddle line of the centre of gravity, above found, of the displacement

7 tive sections, multiplied by the fraction

î

L being half-breadth plan, and through the points of inclosed by the extreme sections, and that they the distance between any two vertical sections, dicular to the upper edge of the rabbet of the only to find the moments of the appendages

division let transverse sections be drawn perpen- are parallel to L. W. L. and section 1, then we have measured on a horizontal section, and I the dis- keel; these sections will, of course, coincide with about on and oy. tance between them measured on the middle line those before drawn, but since the common interval of the half-breadth plan ; the true area of any is measured on the horizontal sections, the true the centre of buoyancy without the appendages

On reference to the table it will be found that horizontal section may therefore be readily found

areas of the horizontal sections will be found on is 4:3115 feet from the L. W. L. and 86.69 feet from these areas given in our table. Generally, the table, and not their projections as before. from section 1; consequently the centre of gravity

1 however, the fraction is so near unity that the Again, the common interval between the hori- of the keel piece is 12:5—4:3115, or 8.1885 feet I

zontal sections must now be measured perpen- from the L. W. L.; therefore 167 ~ 8.1885 = 1367-5 areas found in the table may be taken as the true dicularly to them, and not along the transverse is the product of its weight and distance from areas of the sections, without any practical error ; sections, as in the former case; it is easy to see, ox, also 6.25–4:3115=1.9385 is the distance of and it is only in cases in which the difference of therefore, that the true displacement will in the the centre of gravity of the rudder and posts from draught of water forward and aft is very consider- end be arrived at by the horizontal sections. o x; and 9:5—4:3115=5:1885 is the distance of able in proportion to the length of the ship, that To proceed with the transverse sections we shall | the negative portion forward from the sanie axis,

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therefore 65 x 1.9385=126.0, and 22:8 x 5:1885= | CAPTAIN COLES' PATENT SHIELDS FOR The aperture L is only sufficiently wide to allow 118-3; the sum of the positive products is 1493-5,

ORDNANCE.

the muzzle of the gun to pass through it, but is and the negative product 118-3, the result will CAPTAIN COWPER Puipps COLES, R.N., has re- of sufficient size vertically to allow of the deprestherefore be positive, and equal to 1375.2. This cently patented an apparatus for defending guns sion and elevation of the piece. A narrow aperquantity divided by 28407, the total displacement and gunners in ships of war, gunboats, and land ture l is continued up from the main aperture L, in cubic feet, including appendages, will give batteries. His invention consists of a large con- to admit of the gunner " sighting” the gun with •0485 feet for the distance of the centre of buoy vex shield covered all over its exposed portion with ease and accuracy. When the shield is formed ancy below that corresponding to the displacement thick iron or other metal, and mounted upon a and fitted as shown in the engraving, the ammuni. between the extreme sections, or the centre of platform or frame which is capable of revolving tion must be supplied through an aperture made buoyancy below L. W. L. is 4.36 feet. In a similar after the manner of a turntable, and which also for the purpose in the rear of the shield. But in manner, the distance that the centre of buoyancy carries the gun upon any suitable carriage. An some cases, as on board ship for example, Capmoves aft by the addition of the appendages may aperture is formed in the shield to allow the tain Coles prefers to employ a hollow cylindrical be found to be 34 feet, as given in the table. muzzle of the gun to pass through' it, and this casing in place of the solid central bolt or stud D, The centre of buoyancy is therefore 87.03 feet aperture is somewhat larger vertically than hori. and pass the ammunition up from below through abaft section 1, when the appendages are taken zontally in order to admit of the elevation and it. In like manner he proposes in other cases to into account.

depression of the gun, the lateral aim being modify other details of the apparatus. Instead The student will now, we think, be able to secured by the rotation of the platform. Captain of making the shield of an arched or curved form, make the ordinary calculations for any ship, with Coles does not limit himself to any precise form for instance, he makes it polygonal horizontal either of the usual horizontal planes for the plane or mode of construction, but he usually prefers to section, and straight-sided in vertical section, or of projection, and in the above example he will make the shield hemi-spherical, and to construct it of any other prismatic or other form, which complete for himself the drawing containing the of a wooden frame with timbers in vertical planes will present a convex or inclined surface through. scale of displacement, the scale of the area of the placed close together, the whole being covered out to shot and shell. He likewise sometimes midship section, and that of the tons per such with thick iron plates. In the engravings here- mounts the shield upon spherical balls, or rollers, immersion similar to those given on page 298, unto annexed, we have illustrated the manner in or otherwise, instead of upon the conical rollers vol. I., for our first example.

which he carries his invention into effect. The before described, and in place of the hand wheel

figure is a transverse section of a shield, constructed and gearing for rotating it, he employs any other MONSTER TROOP STEAMER.—The following according to his invention, and adapted to a land suitable appliances for the purpose. Further, he paragraph has been communicated :— Messrs. fort or battery. The body of the shield is com- provides for the escape of smoke from the shield, Pearse and Co., Stockton, have on the stocks for posed of a compact framing of timber A, the whole and for its ventilation, by forming apertures in it the Government an Indian river steamer of im- exposed upper portion of which is covered with for the purpose, and sometimes (as where a central mense proportions. Her length in the water-line thick iron plates B. The shield is built upon a upward passage is provided for the ammunition) is 350 feet, over all 375, and breadth 46 feet. revolving timber platform or frame C, which by forcing air continually through the shield by She is by far the largest river steamer in the world. turns about a central bolt or stud D, and runs means of a fan placed beneath it. Finally, he proHer engines are 200 horse power. She will be upon conical rollers E, placed beneath it near its poses to form the shield large enough in some impelled by paddles, and will, it is expected, attain circumference. These rollers are carried by arms cases to cover two or even more than two guns a speed of 13 miles an hour. She will be fitted | F, which are attached to a loose running central side by side and parallel to each other. When the with sleeping berths and every suitable sanitary ring G. The conical rollers E, run upon a me- shield is employed on board ship it should be arrangement for about 800 soldiers. She will be tallic rail or tram, supported by a foor or platform either built or placed somewhat eccentrically in guided by two large patent steering blades, and H. The rotary motion which is requisite in the order that the common centre of gravity of the shield is made to draw only two feet of water, even with training of the gun is obtained by means of a and the gun or guns beneath it may be caused to all her stores, fuel, and 800 passengers on board. hand-wheel I, fitted within the shield and con- fall in the centre, about which the whole rotates. She is flat-bottomed of course, and weighs about nected with gearing, which works a pinion K, This will prevent the same from having any dis370 tons. She will be completed in about a month, that travels round in teeth or cogs formed upon position to rotate imparted to it by gravity as the and will then be fitted up on the Thames, in order the circumference of the metallic rail or tram. I ship rolls or pitches. Captain Coles prefers to to make an experimental trip.

is the aperture through which the gun protrudes. mount the guns placed beneath the shield upon carriages resembling that invented by Mr. Mar- the cylinder capacity is so great as to admit of the hot uptakes pass up through the steam, the ecoshall in 1827, but modified to suit the purpose steam being expanded to within two pounds of nomy of expansion has never been questioned, but inore effectually. We have no account of the the pressure in the condenser at the end of the can be substantiated to a considerable extent at manner in which this modification of the carriage stroke, while the engines are working full power; any time. It is likely, however, that were the is to be effected, and have consequently had en- and as the nominal power of these engines is con- temperature of the steam from such boilers ascergraved within the shield a gun and carriage tracted to be 320, the cylinders are 90 in. diameter, tained, it would be found considerably superheated. taken from Commander Marshall's original de- and 5 feet stroke; and, in order to reduce the And the use of the various modes of superheating scription of 1827. The following account of this violent shock of high-pressure steam on such a has been rendered much more necessary than it part of the engraving is derived from the same large piston, and also to increase the jacket sur otherwise would have been, by engineers genesource. “A is the breech carriage, which differs faces, a cylinder of one-third the size, or 25in. dia- rally following that type of tubular boiler used by only from the ordinary carriage in its shape before, meter, and 5 feet stroke, is placed close to it. This the Admiralty where there are low steam chests, which will be understood sufficiently by the draw. small cylinder receives the steam direct from the and short uptakes, said to be rendered necessary ing; B is the coin ; C is the trunnion, and D boiler during one-third of its stroke; this steam in the case of the Admiralty on account of expothe asp over the trunnion; E, is the muzzle car. is consequently reduced to one-third of its original sure to shot. riage, having its wheel or wheels F, in this posi- pressure at the end of its stroke, and then enters From the foregoing it is also conclusive that tion at right angles with the wheels of the breech the second cylinder, where it is expanded three with the ordinary construction of steam-engines carriage; E is a mere solid block of wood; G, H times more, making a total of nine volumes. Thus afloat, that small engines going fast would conare two plates bolted to it with eyes at one end r 42 lbs. steam is expanded nine times, or to 13 lbs., sume less coal per indicated horse-power than and t, to receive the hinged bolt J; this bolt namely, from 42 lbs. to 14 lbs. in the small large engines going slow; but with engines such passes through another eyes, which is bolted to cylinder; it then enters the large cylinder at as those of the Callao, Bogota, and Lima the the ship's sides and steps into a socket made for it 14 lbs., and is expanded to 43 lbs., but as the converse will be the case, carried, of course, to in the water ways; K represents the ship's side, second piston is three times the size of the first, within moderate limits. and L the water ways, and n the socket; N is a the gross load will be the same on both pistons, and Again, to return to the case of the Callao, Lima, strong iron crutch, with a piece of hard wood i, i, the piston rods, crossheads, and connecting rods and Bogota, the general construction of the enfitted in the middle of it for the muzzle of the gun may be duplicates of each other.

gines and boilers are as follows:- The cylinders to traverse upon ; this crutch turns on the central From the above pressures of steam at the enter- are four in number, namely, two of 52 inches bolt or pivot P, which is set into a socket made ing of the cylinder, it is evident, that unless the diameter, and two of 90 inches diameter and 5 for it in the block or bed of the muzzle carriage inside surface of the large cylinder is retained feet stroke. The cylinders lie diagonally to each E; the gun is here supposed to be run out in a about 210 degrees, condensation of the steam on other. The steam and eduction valves are wrought straight direction for firing, and if it were fired entering is certain, and such condensation will with eccentrics, the steam valve is a gridiron the recoil would cause the gan to run in the chiefly evaporate into the condenser while the valve with a large lap; one eduction valve serves muzzle, and traversing on the wood i, i, till the eduction port is open, and the latent heat neces- as eduction for the high and its corresponding cratch came to the muzzle rim, or beyond it if re. sary to evaporate such condensation will be much lowepressed cylinder; it has no lap, and the edgequired according to the lengths of the ropes or greater than what would have radiated from the tion port remains open during the entire stroke breechinga. By this arrangement a hand spike or hot cylinder to the condenser, had no con lensa- of the piston, thereby giving a free egress for the tackle applied to the muzzle carriage at x, on tion taken place ; and such heat would be entirely steam, and ample escape for water should it form. either side, will point the gun with the greatest lost. In the same manner it might be mentioned, In reversing the engines the eccentrics are nicety and facility, the wheel or wheels being, that the inside surface of the small cylinder made to overrun the engines by a donkey-engine as will be observed, in the proper position for should be retained as high in temperature as the till they arrive at the backing position-a plan that movement.” It should be observed that the steam that enters it; and in order to attain this which is less likely to cause accident than the characteristic feature of Commander Marshall's car. object every effort should be made in the construc. ordinary methods. This donkey-engine has been riage consisted in mounting the breech and muzzle tion of steam machinery. It is evident that, for found to be most satisfactory in its application. of a gun on two separate carriages, one supporting the small cylinder, superheated steam is absolutely The boilers are tubular, two in number, with the breech and the other the muzzle, and the wheels necessary for this purpose, either in the jacket or iron tubes. Each boiler has three furnaces, 3 feet. of one being at an angle with those of the other. cisterns of the cylinder ; and in the large cylinder 4 inches wide, and 6! feet long, or making an

the temperature of steam direct from the boiler aggregate of 130 square feet of fire-grate. The

to the cylinder may be sufficient, if communicated tubes are of iron, 288 in number, 4 inches inside DOUBLE CYLINDER EXPANSION MARINE through a large enough pipe or aperture. diameter, and 6j feet long. Each vessel has an ENGINES,

In the engines under description the pipe sup- oval steam chest, 12 feet high, and feet long At last year's meeting of the British Association, plying steam to the jackets was 24 in. diameter, and 5 feet broad, with three uptakes through this Mr. John Elder, Engineer, of Glasgow, gave a

and the steam was superheated to upwards of 400 steam chest each 2 feet diameter and 15 feet long.. description, with plans, of the various double degrees that entered the jacket. It was found This makes a strong form of take-up where it joinscylinder expansion marine engines for ocean steam that a large supply to the jacket saved a vast the tube plate, especially in boilers firing across ships that had been constructed by his firm dur- quantity of heat, which can only be explained by the ship; the feed-pipe of the boilers enters into ing the last six years. At the late Aberdeen the principles above mentioned, namely, that any a long flat tank or shield in front of the furnaces meeting he added those of the Callao, Lima, and quantity of heat supplied to the jackets assisted in which the furnace doors are formed. This Bogota, together with those of some others now in proportion to the quantity of latent heat it shield forms a protection to the firemen from in progress. Before entering on this subject he saved being evaporated to the condenser during heat, and makes the heat, otherwise lost, avail

. reminded the Association that these engines are the eduction of the steam, and if the pipes to the able for the feed-water. In the Callao there constructed with the view of getting the greatest jackets were large enough, or sufficient to prevent is a third coil of feed. pipe in the funnel, to amount of power from a given quantity of steam, the condensation referred to, the economy of the heat the feed-water. Such, then, are the leading at a given pressure, with less total weight of machinery was realized to the greatest extent. features of this machinery, and the results are as engine-boilers and water, and occupying less total

Mr. Elder called the attention of all parties con- follows:space than that occupied by the ordinary class of cerned to the performance of Cornish pumping This plan of the boilers gave steam to the ensteam-engines on board of steam-ships. At the engines, and more particularly to the similarity of gines superheated to about 400 degrees by the former meeting he had mentioned that the above action of the steam jacket in these engines to the uptakes, showing that the various systems of steam-ships, with the ordinary first-class system principle of that of the double cylinder engine superheating are unnecessarily complicated : inof machinery, were coming from Valparaiso to with steam jackets. In the Cornish engine the deed, in the Lima, the steam got so far above 100 this country to have their engines replaced by piston it is single acting, and the jacket has twice degrees, that in the Bogota the steam chests were these double-cylinder engines, entirely for the the time to do its work, or rather the steam in the made two feet lower, and two small feed-pipes purpose of saving of fuel-the Lima and Bogota. cylinder is wice the time in contact with the were made to feed the boiler when too much superThey are of the following dimensions :-Length, jackets that it is generally with Watts engine, heated by the tap of the steam chest. The super245 feet; breadth, 36 feet; depth, 23 feet; breadth also that the Cornish engines have very large heated steam, though upwards of 400 degrees of between paddle-boxes, 86 feet; tonnage, 1,650 jacket surfaces in proportion to the power deve- heat, was found quite inadequate to prevent com tons. These ships had formerly'a full poop and loped. With these features in view, the engineers densation in the cylinder, without the steam-jacket forecastle, which were altered this year into a spar constructed the engines now under discussion, and cock being full open. deck, and the hulls of the ship increased in weight to this cause may be attributed a considerable por- Mr. Elder pressed this fact on notice, as in the about 120 tons ; the cabin and hold accommodation tion of their success, and to the non-observance of case of double-cylinder

engines it is so prominently was lengthened 30 feet by the space saved by the these features the almost total failure of economy observed, by comparing the respective diagrams smaller quantity of coal and boiler space required in the expansive working of most steam engines of the low and high-pressed cylinders

, especially for the new machinery; and the registered tonnage on board

of steamships, namely, by constructing as those engines, where the cylinders are so close of the ship was increased by upwards of 400 tons. large engines, going slow, without steam jackets, or that the diagrain of one is an exact counterpart The following statements are in the language of superheating of steam ; such engines would, of of the other, when there is no condensation : and Mr. Elder.

course, present a most favourable opportunity for it is somewhat curious to observe, while taking In the engines of the Lima, Callao, and Bogota, improvement by adding any mode of superheating diagrams of the low pressure cylinder, the apparatus,

gradual development of the diagram, with the • We here preserve Mr. Marshall's language, but without

In the Cunard line, and many of our ocean jacket-cock full open, compared with that when it reproducing the letters of reference in the engraving, steamers where very high steam chests and large ) is shut.

TO THE EDITORS OP TIE

When the steam was at a pressure of 21 pounds will be found on reference to the Report of the in the MECHANICS' MAGAZINE that portion of my above the atmosphere the temperature at the Committee on Steamship Performance, presented essay which relates to the superior capabilities of surface of the water was 264 degs., and at the top to the Association a few days ago, that all the large as compared with smaller vessels; and I take of the steam chest 400 degs. Faht., showing that dimensions and particulars of performance of the the liberty of enclosing a copy of this paper the steam was surcharged to the extent of 136 Lima are embodied therein.

in the hope that you will publish it in the degs., notwithstanding that the steam was in The recorded performances of the Lima was not MECHANICS' MAGAZINE at your earliest convedirect and unimpeded contact with the surface a mere measured mile trial, which may always be nience. As to Mr. Cheverton having understood of the water. The engines made during the made to appear more favourable than practical that I am not the original discoverer of the fortrial trips, which were generally half-a-day in experience afterwards attains, but was such an mula referred to, I presume that he got that length, from about 23 to 26 revolutions, and in- extended trial as the committee had previously information from my own writings. dicated from 1,000 to 1,300 horse-power during recommended, and which recommendation was I am, Gentlemen, yours very obediently, that time, and consumed from 20 to 25 cwts. per adopted by the Directors of the Pacific Steamship

CHARLES ATHERTON. hour, with the surface blow-off cocks open. The Company, the owners of the Lima.

Woolwich Dockyard, 14th November, 1859. Callao, Lima, and Bogota have all shown a consumption of from 2 to 2 pounds per indicated

SILAS'S MARINE LIGHTS.

SHIPS' CHAIN CABLES. horse-power per hour best Welsh coals, and the MR. FERDINAND SILAS, inventor of the indestruc

MT-Nov. 10, 1859. speed of the ships from 124 to 13 knots per hour. tible lights applicable for telegraphic purposes at

MECHANICS' MAGAZINE."

GENTLEMEN,—Your correspondent “Amicus," in between Valparaiso and Panama with Her Majesty's sea, and also to point out the presence of life-buoy: in connection with the destruction of the Royal mails for upwards of nine months, and has pera .

were exhibited for the
approval of the Lords of Charter, has done much good, by enlightening

the

public upon the character of the iron plates used The distance between these is upwards of 3,200 the Admiralty in September last, in the presence in the construction of iron vessels. There is miles, and this she performs regularly on about of Commodore the Hon. Sir James Drummond,

one point, however, upon which his exposition 300 tons of coals. The Callao made the run from C.B., and the officers of Woolwich Dockyard, last is imperfect. ' I refer to the quality of the iron Liverpool to Valparaiso in, I think, about 36 days night performed a course of experiments at Black: used in the chain cables, and I pray a short space

wall for the satisfaction of Admiral M‘Hardy, Capt. for a few lines on that subject. steaming time, which averages about 240 miles per F. R. Ward, members of the Royal National Lifeday during a run of 9,000 miles on a consump. boat Institution Committee; Capt. Robertson, lation of the destruction of the Royal Charter is that

The first misfortune that we read of in this sad retion of about 20 cwts. per hour. The Lima has also arrived at her destination after a most suc

Surveyor-General; Mr. Lewis, Secretary ; Mr. cessful run; she performed the distance of 1,500 Grey, and other members of the Board of Trade after the anchors were cast the two cables snapped.

The readers of the graphic article in the Times, miles, from Valparaiso to Callao, in 141 hours, at six o'clock, when a number of the floating lights, to have their memories refreshed how the cables did who were present. The experiments commenced

“ The Great Eastern in the gale,” will not require consuming 150 tons of coals, logging at an average of 260 miles per day during that distance , attached to lines, were cast into the river from duty in her case. We read~" In this

last struggle the pier. considerably faster than she had ever done with her original engines, and on less than half the phoric substance of which they are composed sud- some of the links of the chain cable were actually

dragged out one-third longer, and one, which coals consumed. The Bogota was completed and denly burst into a blaze of light, and was only passed under the sharp bows of the vessel, was tested on the first of September last, and found extinguished by being dragged under the water bent nearly double.". fully equal to the others. She made the run from The apparatus intended for the telegraphic light

This was

It is the writer's opinion had the Royal Charter the Cloch Light in the Clyde to the Hell Buoy at resembles a moderator table-lamp. Liverpool in 15 hours, against a strong head placed on the jetty near the water's edge, and cables been of the same quality as those of the Great wind, and consumed during that distance 15 tons the opaque fog, which completely enshrouded the lost. I have heard it stated and repeated that the was operated upon by the inventor. In spite of metal and more precious lives would not have been

Eastern that vessel and her cargo of precious of Scotch coals.

river from bank to bank, the strong glare of the At the Admiralty trial, which took place im. mediately on her arrival at Liverpool, she averaged phosphoric light penetrated for some considerable proprietors of large vessels care not anything forupwards of 13 knots , the engine made 254 revolu- distance, and was gratefully acknowledged by they stand the test required by the insurance

several boatmen, who would otherwise have had offices. A very common or inferior iron cable will tions; she indicated 1.080 horse-power, and consumed about 21 cwts. per hour of Scotch coals; great difficulty in making the pier. Similar experiments were entered into a few days ago in the be received then, although the cable may not have

stand that test, when new. Yet such a strain may the steam was superheated to 340 degrees on entering the cylinder, and the thermometer at the presence of Admiral Gordon and the Brethern of snapped, that it would have been far safer to have water level of the boiler showed 264; the

House, together with the officers of the in the boilers was 27 lbs., and the vacuum in the exploring ship Fox. It was then pronounced that used the cable without testing it. But with a the invention was extremely suitable for all the whatever is done to the cable by the test employed,

superior quality of tenacious fibrous iron, no injury condensers 26 inches. She left Liverpool for Valparaiso on the 11th of the present month, with purposes-above named, but they could not recom

and it would not be torn asunder without almost sufficient coals to carry her 6,000 miles at 240 mend the apparatus as applicable for lighthouses. double the weight employed. I have spoken miles per day, and a full complement of stores for the passengers on board; her draught of river was last night involved, and the difficulty of myself to cable manufacturers upon the imwater on leaving Liverpool at the load line was,

propriety of using common No. 2 bolts for thoroughly carrying out the experiments, it was aft, 14 ft. 6 in.; forward, 13 ft. 9 in.; and dis

arranged, at the request of Admiral Hardy, that making cables, and have received some such a second course of experiments shall take place at and used the iron of the best makers.

as that they received no complaints, placement, 1,700 tons. She steamed to the

Is Holyhead Light, where the pilot left her, at the Blackwall on some future occasion.—Times.

there no one to complain for the host of lives, rate of 117 nautical miles per hour against a

as valuable as our own, which have been lost in strong head wind; the engines were making 20

STEAM SHIP ECONOMY.

the last fortnight's storms from this cause ? I revolutions; the steam pressure was 26 lbs.; the TO THE EDITORS OF THE “ MECHANICS' MAGAZINE.' know nothing of the cables of the Royal Charter, vacuum 26 inches; and the consumption of coals GENTLEMEN,-Mr. Cheverton, I believe, admits but cannot help forming an unfavourable opinion 22 cwts, best Welsh coals per hour.

the applicability of the formula based on the mid of them, and suppose them to be no better than The engineers are now constructing the ma. ship section (Ă); it therefore appears to me that the plates employed. chinery for three other steam-ships on this prin. he cannot object to my making use of this same The cables of the Great Eastern, as has been ciple, with boilers on the cellular cylindrical spiral formula expressed in terms of the displacement stated, were made by Messrs. Brown, Lenox, and principle. In conclusion, the form of engines now (DI) unless he is prepared to question the geo. Co., Cardiff, and of iron prepard for them at the described gives regularity of motion, while work. metrical fact that the corresponding sectional works of Mr. Anthony Hill (Hill P F Co.); and ing expansively to the fullest extent, the expan- areas of similar bodies vary as the square of the the late Mr. Brunel had most emphatically resion principle is fully realised, and the engines are cube root of the cubical contents, that is, when quested Mr. Hill, that the best possible iron only of a strong architectural figure, with the various applied to shipping the midship sectional areas of should be provided,—and probably better iron was parts easily got at, and reduced to simple forms, the immersed bodies vary as the square of the never seen than that used in the cables of the and present every facility for reversing freely by cube root of the displacements. As many of your Great Eastern, and it was not a bit too good, as the engine-driver.

readers are now taking an interest in the theo the proof as shown. The performance of the Lima on a trial trip of retical performances of large ships in the reason- Allow me to close this subject in your own considerable distance, namely, between Liverpool able hope that the Great Eastern will afford the words. “This state of things should be remedied. and Dublin, was made several months ago, under opportunity of practically testing the value of In the name of Christian charity, let us not expose the observation of a member of the Steamship such theoretical calculations, and as the essay our fellow.creatures to violent deaths, 500 at a Performance Committee, appointed by the British (Steam Ship Capability, 2nd edition) to which I time, for the mere difference in the price per ton Association at its last meeting at Leeds.

made reference in my letter of the lst instant, between good and bad iron.” “VERITAS.The member watched the performance of the being now out of print, is not readily acship and her machinery with the utmost minute cessible, and as the promotion of public dis.

TO THE EDITORS OF THE “MECHANICS' MAGAZINE,” ness, in conjunction with the Admiralty engineer;cussion, with a view to public utility, is the GENTLEMEN,– I feel assured you will pardon me and an accurate return has been made to the com- oniy object that I have in publication, you for bringing the attention of the public through mittee, in accordance with the form prescribed would do me a favour, and perhaps some of your your columns to the apparent ultimate cause of and recommended for general adoption ; and it correspondents an acceptable service, by inserting the loss of the noble steamer the Royal Charter

answer

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