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it approximates to that shape. Its curvature is determined by the constructor with regard to the required fulness of the after-part of the deck. The knuckle line forms, as we have said, the base of the stern, which is strictly a conical surfacethis line being the directrix. The fixed point through which the generating lines are to pass is at the height required to give the inclination of the lights just spoken of, and it lies also in the prolongation of the line defining the rake of the stern, or of the after-boundary of the sheer plan. The point thus found is the vertex of the cone which envelopes the stern.

Those portions of the outer edges of the stern timbers which lie above the knuckle, and in the co

nical surface, are straight; and their projections on both the planes of projection are, therefore, straight lines, but below the cone they follow the contour of the buttock. As the planes in which the sides of these timbers lie pass through the vertex of the cone, they are necessarily inclined to the horizontal plane, and the horizontal projections of the curved portions of the edges of the timbers will therefore be curved. If these inclined planes are parallel to the axis, as they are in some cases, the vertical projections of the curved portions of the edges upon the body plan will be straight lines -continuations, in fact, of the projections of the upper parts; but, if the planes cant inwards, then the projections upon the body plan, as well as upon the half-breadth, are curved below the knuckle. The former of these cases but rarely When it does, the mode of finding the true shape is very simple. Draw in the body plan, in the required position, a straight line, leading up to the vertex of the cone, and cutting the level lines below the knuckle. Measure the distances of its points of intersection with the sheer lines and level lines from the middle line,

occurs.

and set them off in the half-breadth on the corre

sponding lines, by which means the horizontal projection may be obtained. Then square up these same points into the sheer, and obtain on that plane another vertical projection of the moulding edge of the timber. Now, suppose the plane containing this moulding edge to be swung round a horizontal and fore-and-aft line passing through the knuckle until the plane is parallel to the sheer plane. In this revolution every point in the edge of the timber will move vertically-those above the knuckle upwards, and those below it downwards. Those points, therefore, which have been projected on the sheer plan from the sheer and level lines, will be found vertically over or under their projections, and at distances above or below the knuckle equal to the distances of their projections on the body from the intersection at the knuckle. On joining the points so formed we obtain the true shape of the nonlding edge of the timber. Proceed in the same manner to obtain the projection of the bevelling edge on the sheer plan, remembering that in the revolution the plane of the bevelling edge must turn about the same axis as that of the moulding edge, so that the distances to be set above or below the knuckle to obtain the true shape must be measured, not from the point in which the projection in the body cuts the knuckle, but from a line, drawn from the point in which the moulding edge cuts the knuckle, and square to the projection of that edge. Sometimes there is an angle in the side of the timber at the knuckle, and the lower part of the timber is parallel to the sheer plan. The vertical projection of this portion of the timber would then, of course, be the true shape.

In the second case-i.e., when the side of the timber is canted - the problem becomes more difficult. According to the only mode that has ever been adopted for laying them off, the positions of their heels cannot be determined beforehand, so that it is difficult to make a good arrangement of the timbers with regard to the short cant timbers below upon which they have to abut. Partly on this account, and partly also as a means of getting better conversion by using timber with a side curvature, the positions

of the timbers of the stern are sometimes deter-
mined at the ship, and moulds are made there with-
out the aid of the draftsman. This much, however,
is certain, that the side of the timber can always
be so canted as to bring the heel wherever it is
required. Sometimes the cant necessary for this
purpose may give too great bevelling to the
timber. Should this ever be so, the timber must
be cut with a side turn. In such a case the drafts-
man's art fails. But it is believed to be always
possible to make a good arrangenent of the stern
frame with straight-sided timbers. Let us pro-
ceed to show how this may be done. The method
in use will be given afterwards.

we seek must pass through 0, or, which is the same thing since O is in the plane of projection, through o', its vertical projection. If, therefore, we join k'o', we have the line B', the vertical trace required. It will be seen that the plane BB cuts the planes I., II., III., in straight level lines starting from n', k', and p' respectively. That through ' is coincident with the trace B, and the others are parallel to it. The horizontal projections of these lines will evidently be nr, kh, an l pq. The lowest of these lines, pq, lies in the same plane as the level line III., and since it also lies in the plane B B', the point q in which it meets the level line, is in their intersection, and is therefore a point in the required edge of the timber. Similarly, h and r are points in this edge; d and c we already know to be so. Join d, r, h, and q by a curve, and we have the horizontal projection of the moulding edge of the timber. So also by means of the plane A A', we obtain bv, the moulding edge of the outer timber, as we might also that of the inner timber by means of the plane C C. To find points in the vertical plano corresponding to these, we have only to set off corresponding breadths on the several lines, by which we obtain as the vertical projection of the moulding edge c', d', ', h' q'. The points u and u, corresponding in like manner, give the ending of the edge at the side of the cant.

New Mode of Laying-off Canted Timbers.In the diagrams before us, the vertical plane of projection is taken a little on the fore-side of the knuckle; and the horizontal plane of projection is made to coincide with the plane of one of the level lines (No. II.), for a purpose which will be apparent as we go on. On these two planes, we have the projections of the knuckle and roughtree lines, and of the level lines I., II., III. Let (a b, a' b), (cd, e' d'), and (ef, e'f') be the upper portions of the moulding edges of three stern timbers. These portions of the projections of the timbers are obtained by fixing their positions on the knuckle, and drawing lines in both plans, leading to the projections of the apex of the cone. We must now proceed to find the projections To discover the true shape, the plane containing below the knuckle, for which purpose it will be the moulding edge must be thrown down upon necessary to discover the traces on the two the vertical plane of projection about the vertical planes of projection of the plane of the moulding trace-in this case therefore, about B'. During side of the timber. Take, for example, the middle the revolution the points of which c', d', r', h', u', one of the three timbers shown; then we must and q' are the projections, will describe circles at find a plane which contains the line (ed, c'd). right angles to the line B', and will fall in lines The horizontal traces of all the planes which drawn through these points at right angles to B'. satisfy this condition must contain or pass Consider now for a moment the level plane III. through the horizontal trace of the line, and Both P and Q, of which p' and q' are projections, their vertical traces must contain the vertical lie in this plane, and their actual distance from trace of the line. Produce cd and e' d'-g' will each other is p q, seen in the half-breadth. In the then be the vertical projection of the horizontal revolution, P being in the axis, does not move; trace of the line, and g, obtained from g', its hori- the point will therefore be found at a distance zontal projection. Similarly, i is the horizontal from the axis, or from p', equal to p q. Take then, projection of the vertical trace of the line, and i', in a pair of compasses, the length p q, and sweep obtained from i, its vertical projection. The horia circle from p', cutting the square line through zontal and vertical traces of the plane must there-in Q, and Q will be a point in the moulding edge. fore pass through g and respectively. There Set off similarly k H, equal to k h; n' R (Ris are evidently an infinite number of lines which omitted in the figure) equal to n r; m' D equal to could be drawn through these points, as there are md; and o' C equal to o c; join these points, and an infinite number of planes which could be we have the true shape of the timber. In setting drawn through (ed, e' d'); and it is necessary to off the distances for the knuckle and roughtree, it decide upon the direction in which the plane of must be observed that a line drawn from (d, d') in the side of the timber shall lie. The horizontal the plane of the moulding edge and parallel to trace may be drawn, if we choose, at right the horizontal plane, will meet the vertical trace angles to the curve of the knuckle: in which of the plane in m', below the curve. And that case the horizontal section of the timber at similarly a horizontal line drawn from e c' in the the knuckle would be square; or it may be plane of the moulding edge will meet the plane of desirable to bring the heel of the timber upon the projection in o'. It is therefore m' and o', and head of the cant timber, s, without regard to the not points in the curved lines themselves, which bevellings. In that case mark a point, h, upon correspond to m and o in the half-breadth, and level line II., in such a position that a line passing from which the distances must be set off. through d and h may fall on the head of s; then if the line B be drawn through g and h, the horizontal projection of the edge of the timber will also pass through h, because level line II. is in the horizontal plane of projection. The line B, thus drawn, is the horizontal trace of the plane of the moulding side of the timber. The angles which it makes with the sheer and level lines indicate the bevellings which the timber will have in horizontal sections at those heights. If they are found too great, it must be concluded that the heel of the timber cannot be brought upon s. To obtain the vertical trace of this plane, observe first, that it must pass through , and that it must meet the axis, LT, at the same distance from the middle line as B does, (i.e.) Lk must be equal to L k. These two points are, however, too close together to define the line B' accurately; observe, therefore, that if a horizontal line, CO, were drawn from the point cc', in the plane of which B is the trace, its horizontal projection would be c o, and its vertical projection co'. But the point O must be in the line of intersection of the plane of the side of the timber and the plane of projection, in other words, the vertical trace

BREECH-LOADING SMALL ARMS. CAPTAIN NORTON writes:-"To the Editors of the MECHANICS' MAGAZINE. Gentlemen,-I am happy to be enabled to inform you that breech-loading sporting guns may be made available as military arms in case of emergency, simply by using gossamer cartridges, and a close-fitting spherical bullet enclosed in proved this day at Mr. Riley's shooting-gallery, 315 a thin greased patch of cotton net; this I successfully Oxford-street, W. The young man attending there fired three blank cartridges in succession without failure; the felt wad, forming the head of the cartridge, carries the unconsumed portion of the thin tough paper and cotton net clean out of the barrel at every discharge. The American civilians did good service with their smooth-bore sporting guns at the battle of of using sporting guns, England could instantly comBunker's Hill. By following the above-described plan mand the willing services of a million ready-trained and well-armed guerillas of native growth, and racy of the soil. Your obedient servant, J. NORTON. Rosherville, 23rd August."

It is expected that the Mersey, 40, screw frigate, at Spithead, will shortly receive several of Sir W. Armstrong's guns, in addition to her present armament.

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THE HYDRAULIC LIFT AT THE VICTORIA DOCKS.

Invented by Mr. EDWIN CLARK.

ON Wednesday, the 27th of July, many who are interested in the progress of science had the pleasure of seeing in successful operation at the Victoria Docks Mr. Edwin Clark's method of ship-lifting, which appears likely to supersede the graving dock for many purposes. Mr. Clark's apparatus consists of a series of thirty-two upright hydraulic rams, of ten inches in diameter, placed in a waterway in two lines of sixteen each, far enough apart to admit of a ship of any burden passing between. Each ram is fitted with a crosshead of wrought-iron, and the crossheads are supplied with long straps, to the lower end of which are connected girders extending across from row torow. These girders, when the rams are down, are of course at the bottom of the water. The pontoon, on which the ship is raised, is formed of wroughtiron plate, strongly ribbed, the length and depth of which varies according to the size of the ship it is intended to lift. This pontoon is open at the top, and is of sufficient buoyancy, when empty, to support a vessel of very large tonnage. It is fitted with screw valves for admitting the water, so that in a very short time, when placed in position, it can be lowered down upon the cross

girders. The rams are fed by a 50 lb. engine,

which is fitted with twelve hydraulic pumps, 13th in. diameter, and 2 ft. stroke, working at 18 strokes per minute, and the pipes from these pumps, before branching off to the rams, communicate with a series of valves arranged in a place built for that purpose close to the lift. By means of excentrics, which close the valves, any one of the rams can be disconnected at will from the supply, so that should one of the pipes burst, no danger can accrue to the ship, and the lifting process can be completed without delay.

At half-past 1 o'clock on Wednesday, the 27th, the pontoon being placed in position upon the girders, it was first filled and then lowered to the bottom of the water. After this the Jason, a ship of about 1,000 tons burden, was warped in, and having been fixed in position by means of ten sliding blocks, which were pulled into contact with the sides and bottom by means of chains brought above the water line, the engine was set to work,

and the whole mass rose gradually out of the water | A at a speed of one foot in three minutes. As the pontoon came above the surface, it relieved itself of the water it contained, and the valves being then closed, the buoyancy of the saucer itself supported the ship in a perfectly steady and satisfactory manner. The whole operation, from the beginning and the dead weight lifted, including the pontoon, to the end, extended over the space of 14 hours, was altogether above 1,600 tons. There are four struction, which when raised in this manner, and pontoons constructed, and others in course of confloated, are to be towed with their burden into shallow bricked recesses provided for that purpose, so that the hydraulic power can be continuously tainment which followed the experiment, or applied for raising purposes. During an enterhis audience a clear and concise description of his rather the operation, Mr. Edwin Clark laid before invention, and the obstacles he had had to contend with in bringing it to its present state of perfec

tion.

The engraving No. 1 shows a cross section of the lift, with a ship in the act of being raised. AA are two of the columns in which the rams are placed; B shows one of the cross girders; C, the end of the pontoon; D D, two of the sliding blocks for steadying the ship, and EE are two double purchase crabs for raising weights, and about anywhere upon the top platforms, and are lifting the rams when required. These can be run very useful adjuncts.

Engraving No. 2 is a section, in detail, of one of the columns, showing the ram, which is lettered 4, the cross-head B, the side rods C C, and the cap plate D. It will be noticed that the hydraulic cylinder containing the ram rests upon a block of concrete, which fills up the inside of the column to the required height.

It will be needless for us to say much more upon the subject of Mr. Clark's invention. Its superiority over the old graving dock for many purposes is sufficiently manifest. Instead of a vast outlay upon excavations, masonry, and elaborate machinery in each instance, one hydraulic lift will do the work of any number of graving docks; and the only expense, beyond the first outlay, is providing an adequate number of pontoons for the work, and water space of any kind beyond three feet deep for floating them in.

were

on

NEW MARINE LIGHT. COMMODORE the Hon. James R. Drummond and the officers of Her Majesty's Dockyard, Woolwich, gaged in testing a Saturday night last ennewly-discovered light, tophore," intended for denominated "the pholighthouses, and all the purposes of lights at sea. The paddle-wheel charge of Mr. Thomas, steam-vessel Bustler, in the Fisgard, having on master commanding board Mr. Ferdinand Silas, a native of Holland (the inventor of the photophore), left the dockyard jetty at half-past 8 o'clock, and, having hoisted one of the new lights at the mast-head, proceeded slowly down the river while a number of the for a short distance,

instruments passed along the banks were lighted up, the pale red glare of which was from that of all other easily distinguished lights, and was also pronounced to be more brilliant. Commodore Drummond remaining stationed on the jetty directed a course of signals by the constant lighting and extinguishing of the photophore, which was similarly replied to by the inventor on board the Bustler. One of the instruments attached to a line was thrown into the water without being previously lighted, and on rising to the surface it shot forth a phosphoric blaze, which, according to the inventor's statement, would keep alive for 10 or 12 hours.

THE STEERING OF SCREW STEAMSHIPS.

THE difficulty of steering long ships has always been a great impediment to the lengthening of screw steam-ships, particularly in the case of war vessels, which should be capable of performing rapid evolutions. During some recent experiments on board his steam-yacht, the Dragon-fly, Mr. Joseph Maudslay discovered a fact which appears to us to have a very important bearing upon this subject. The screw-propeller of the Dragon-fly is fitted with feathering-blades, which are capable of having their pitch varied with the utmost ease from the deck, either when the screw is at rest or when it is revolving at any speed. The remarkable fact which Mr. Maudslay has observed is, that when both blades are set in the line of the keel-or, in other words, in the longi

tudinal plane passing through the centre of the ship-and the screw is set revolving, the vessel is turned round very rapidly. If, when the vessel is going at a considerable speed, in the usual way, the blades are rapidly brought into the position before stated, she also turns very quickly. We content ourselves, for the present, with placing this fact on record, only remarking that, while it is not difficult to see how it is to be accounted for, it is impossible not to view it as very important.

We subjoin an engraving of Mr. Maudslay's feathering screw (which was published in our Magazine for 1856) in order that the nature of the feathering propeller may be apparent to our readers. A glance at the several figures will make its construction evident to practical

men.

FREE DRINKING FOUNTAINS. TO THE EDITORS OF THE " MECHANICS' MAGAZINE." GENTLEMEN,-In an article on free drinking fountains in your excellent Magazine of the 19th instant, you describe certain arrangements which it is stated the Metropolitan Free Drinking Fountains Association has adopted for the filtration of water at their fountains. As this account is not altogether correct, we beg to be allowed to state that the only means hitherto used for the filtration of water at the fountains of the Association, as well as at various others in the metro

polis, are the filters of the Moulded Carbon Company, designed and supplied by us. The annexed figure will probably afford a better explanation of the arrangement adopted, than that which is conveyed by your representation.

A is an iron cistern containing a hollow cylinder of moulded carbon B, which is suspended to the lid by a nut F, through which the pipe E is passed into the carbon. The unfiltered water enters by the pipe C, which is perforated on its underside within the cistern, and made to surround the cylinder; by this means the water flows continually over the whole surface of the carbon, and prevents the deposition of insoluble matter upon it, which is carried down to the bottom of the cistern, from where it may occasionally be drawn, and the whole cleaned out by opening the tap G. D, tap to regulate the supply. E E are union joints, by which the apparatus can be fixed

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ADMIRALTY EXPERIMENTS ON IRONSIDED SHIPS.

A SERIES of experimental trials have been carried on during the past fortnight at Portsmouth, with a view of ascertaining the amount of resistance offered by iron and steel plates of various manufactures when opposed to heavy ordnance at a short range. The trials are understood to have reference to the future coating of the steam ram now in progress of construction. The practice has been carried on from the Stork gunboat, tender to Her Majesty's ship Excellent, gunnery ship in Portsmouth harbour, both from a 32pounder and a 95 cwt. gun, the latter throwing a solid 681b. shot, with 16lb. charge of powder; the distance of range 200 yards. At this distance the results of the experiments have demonstrated in the clearest possible manner that no iron or steel

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plate that has yet been manufactured can with- turing towns, and in the rural districts; with
stand the solid shot from the 95 cwt. gun at a officers of both services, landed proprietors, mer-
short range. The first shot would not penetrate chants, lawyers, and also with peasants and
through the iron plate, but it would fracture it, artisans, sailors and fishermen. He had thus the
and on three or four striking the plate in the best opportunities of acquiring information, and
same place, or in the immediate neighbourhood, of learning the feelings entertained towards this
it would be smashed to pieces. As the results of country by a great number of Frenchmen.
the trial affected the steel plates it proved that a Although he cannot but admit that he experi-
steel-clothed ship could be far more easily de-enced on no occasion any lack of personal courtesy,
stroyed than a wooden-sided one, and that on the it must still be allowed that if some of the
smashing-in of one of the steel-plates the de- opinions he heard were reproduced at home, in
struction of life on the armed ship's decks, sup- the precise terms in which they were originally
posing the broken plate to be driven through the expressed, our national vanity would scarcely feel
ship's side, would be something dreadful to con- flattered by the sentiments towards us so frankly
template, from the spread of the splintered avowed. With the view, moreover, of fully
material. At from 600 to 800 yards iron-clothed ascertaining the real capabilities and present
ships would be in comparative safety from the condition of the navy and arsenals of France,
effects of an enemy's broadside, but it must be he passed some time at Toulon, at Rochefort,
borne in mind that the effects of concentrated at Lorient, at Brest, and at Cherbourg, care-
firing have yet to be ascertained on the sides of an fully investigating all that had been done of
iron-clothed ship, and account also must be taken late years at those several ports, inspecting
of the damage the woodwork forming the inner the works in progress at each. He was, besides,
sides of such a ship would receive from the fortunate enough to obtain access to important
driving-in of the broken plates; and which, as far and unpublished official documents, so as to check
as the present experiments have illustrated, would the accuracy of oral information. By this means
appear to prove that an iron or steel-clad ship, on
he was enabled to ascertain precisely the present
receiving a concentrated broadside from a frigate, strength of the French marine, the age of every
armed in a similar manner to the Mersey, and ship, the port at which she was built, the number
struck near her waterline, must sink then and of her guns, and in the case of steamers the
there, with her armour on her back.-Times.
horse-power of each. This information, collected
as it is from trustworthy sources, cannot but be
deemed, at the present juncture of considerable
value; and if the jealous care of the French
Government, in withholding such knowledge, be
taken into account, and consequently the extreme
difliculty of procuring statistical facts of the
kind, in a country where not only no official navy
list is published, but where no catalogue of the
sort is allowed to be publically circulated under
any pretence, some estimate may be formed of
the toil necessary to succeed in an enterprise
apparently so hopeless as the one undertaken by
the author. Patient perseverence, however,
overcame all difficulties, and the result of his
labours will be found incorporated in the following
pages. The summary there furnished will cer
tainly afford matter for reflection. That very

Literature.

The Navics of the World; their Present State and
Future Capabilities. By HANS BUSK, M.A., of
Trinity College, Cambridge. With Illustrations.
London: Routledge, Warnes, and Routledge, Far-
ringdon-street. 1859.

WHEN report on report and parliamentary return
on parliamentary return, all abounding in informa-
tion relating to the navy, came pouring forth at the
commencement of the present year,we felt perfectly
sure that some one or other would hash them up
into the form of a volume, with a loud-sounding
title, and have it advertised from one end of the

numerous class of our countrymen who have been

[AUGUST 26, 1859.

altered character of naval evolutions rendered necessary by these changes. He has, moreover, felt called upon to express his opinions upon the apparent inefficiency of the old Admiralty Board in coping with the urgent requirements of the present critical juncture. And, though last, not least in importance, our coast and land defences will be found discussed, if not with adequate ability, at least in a sincere and earnest spirit. In connexion with this latter topic, the author has ventured to call public attention to the great advantage of training a portion of the civilian population to the use of arms, through the medium of volunteer associations, organised under the sanction of Government, so as to be available on an emergency as a valuable reserve."

Busk's volume with the gravity which a profound Although we are not disposed to treat Mr. and well-studied work on the "Navies of the World" would deserve, we would have it understood that the author has not bestowed his labours grudgingly upon it. He has amassed an unex ampled amount of information relative to the French navies and naval ports, and to this he has added useful descriptions of other foreign navies. His detailed lists of our own navy are also very copious and complete, and, so far as we have observed, very accurate also. The volume also comprises a reprint of the "Conversations-Lexicon" article on the English and French navies, together with a spirited review of the same.

naval readers, fail to say that the volume is not But we cannot, in justice to our numerous without serious errors-errors into which none but a purely amateur writer could have fallen. For example, in the detailed statement of the strength of our own navy, we are gravely informed, in a special note, that our three-deck screw ships draw from 35 to 36 feet of water! And, that there may be no doubt as to the deliberation with which these figures are given, we are further told that twenty-two of the two-deck

so very remote from his professional calling, we really are still astonished to find him falling into such an error as this. Ships drawing 36 feet of water may, perhaps, be built by coming generations, but if they should be, they will certainly find entrance into very few of our ports.

world to the other. As Mr. Hans Busk, Master of Arts, Barrister-at-Law, Lieutenant of the Vic-accustomed, from the many disastrous defeats susscrew ships draw about 34 feet; and the rest toria Volunteer Rifles, author of "The Rifle, and tained at sea by France, during former wars, about 32 fect. Now, no naval man need be told How to Use It," &c., is rather fond of getting up to regard her maritime resources as immea- that these are most absurd statements. The ship books apparently, there seems to us no reason why surably inferior to our own, will learn with some which draws more water than any other in our astonishment that, chiefly owing to the enerhe should not have been the man to undertake the getic exercise of her indomitable will, she has navy is the Duke of Wellington, and her draught business; and Mr. Busk himself appears to have been for some time past steadily gathering is about 27 ft. 6 in. aft., and 25 ft. 6 in. forward; thought the same. We are glad he has done so, together her giant strength, and could at a her mean draught being, therefore, 26 ft. 6 ins. because, he failing, the undertaking might have very brief notice, if need were, equip for sea-nearly 10 feet less than Mr. Busk says! After fallen into the hands of some idle person, who a fleet of more than four hundred vessels, of making all due allowances for Mr. Busk's circumwould have performed it far less satisfactorily than which nearly threescore would be ships of the stances, as the author of a work on a subject lying line! At the same time, the whole available strength of England's bulwarks, numerically reckoned, cannot be considered very materially to exceed that of France, and this is especially the case as regards effective line of-battle ships and also, has been to collect authentic information on frigates. One of the author's chief objects, the present condition and future prospects of our own navy; in detailing which, in its proper place, he has ventured briefly to introduce such views and suggestions for its improvement as may have occurred to himself, or have been derived from a careful examination of the opinions expressed by experienced naval men and other competent authorities. A slight sketch of the actual state of the navies of other maritime powers as Russia, the United States, Holland, Austria, Denmark, Sweden, &c.—has also been appended, so as to present, in a compact form, a comparative view of the existing navies of the world.' Besides the above topics, the author has thought it essential to a full elucidation of the subject to devote separate chapters to the consideration of other matters intimately connected with the whole question; such as the application of steam to ships-of-war, and especially the important introduction of the screw; naval gunnery, as based upon the vastly improved ordnance now in use, as well as the

he. Considering who Mr. Busk is, and how very
little he could be expected to know of the world's
navies, he has really done his work astonishingly
well. In order to acquaint our readers with
the spirited manner in which he has gone
about it, we quote the following extract from
the author's preface. In perusing it, let no
reader object to the frank testimony which Mr.
Busk bears to the zeal and the successes of Mr.
Busk. A little fluent freedom of that kind on
the part of an author will not do us any harm-
unless it should become common ! Mr. Busk
says:-
66 An earnest desire to obtain authentic
intelligence on these matters stimulated the au-
thor, during the latter part of the past year, to
visit the several French naval stations, at some of
which he encountered a variety of obstacles, al-
though he finally succeeded in his object beyond
his most sanguine expectations. In the prosecu-
tion of his inquiries, the writer travelled several
thousand miles in France, associated and conversed
with people of various grades and professions, as
well at the military and naval stations, arsenals,
and seaports, as in the large cities and manufac-

There are other portions of this volume which have but little interest for us, but which may be very useful nevertheless to many others, especially

to those who are not readers of the MECHANICS

MAGAZINE. We meet with a good deal that has appeared from time to time, and in various forms, in our columns; such as descriptions of the Armstrong gun, the Whitworth gun, Captain Norton's and Captain Blakely's inventions, Mr. Macintosh's system of warfare, and so forth. We also, we regret to say, meet with not a little loose writing about “ Admiralty jobbery," the "shortcomings of that department," &c. We do not believe that such writing can do any good. We have already plenty of men who are fluent enough in quoting epithets; we want no more of them; what we do want are men who can take up facts

with fairness and impartiality, weigh and balance them with intelligence, and then give us the result of their deliberations calmly, nothing extenuating nor setting down aught in malice.

On the whole Mr. Busk's book may be taken as a useful and timely compilation, and while no one must believe all that it says, many may read it with profit.

LIST OF NEW BOOKS.

Archer's Universal Yacht Signals, 3rd edition, 103.
Catechism of Photography, 1s.

Easton's Examples in Arithmetic and Mensuration, 1s.
Eler's Geology in the Garden, 6s.

Galbraith and Haughton's Arithmetic, Key to, 5s.
Galbraith and Haughton's Mechanics, Key to, by M'Dowell

Galbraith and Haughton's Plane Trigonometry, Key to, 5s.
Griffith's Artillerist's Manual, 8th edition, 78. Gd.
Hartley's Handy Book for Rifle Volunteers, 78.
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| and then annealed, in this way retaining the exterior and first cooled skin of glass. The cubes were cut from much larger portions, and were in consequence probably in a less perfect condition as regards annealing. Hence, as might have been anticipated the results upon the two classes of specimens, although consistent in each case, differ widely from one another.

The mean compressive resistance of the cylinders, varying in height from 1 to 2 inches, and about 0.75 inch in diameter, is giving on the following table ·

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THE STRENGTH OF GLASS GLOBES AND however, that the fracture occurred in vertical CYLINDERS.

planes, splitting up the specimen in all directions. Cracks were noticed to form some time before the specimen finally gave way; then these rapidly increased in number, splitting the glass into innunerable prisms, which finally bent or broke, and the specimen was destroyed.

By W. FAIRBAIRN and T. TATE. The following communication was read to the Royal Society::-"On the resistance of glass globes and cylinders to collapse from external pressure, and on the tensile and compressive strength of various kinds of glass." By William Fairbairn, The following table gives the results of the exEsq., C.E., F.R.S., and T. Tate, Esq., F.R.A.S.periments upon the cut cubes of glass :Received May 3, 1859. We have since obtained the following official abstract of the paper :

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The researches contained in this paper are in continuance of those upon the resistance of wrought-iron tubes to collapse, which have been published in the "Philosophical Transactions" for 1858. The results arrived at in those experiments were so important as to suggest further inquiry under the same conditions of rupture with other materials; and glass was selected, not only as differing widely in its physical properties from wrought-iron, and hence well fitted to extend our knowledge of the laws of collapse, but because our acquaintance with its strength in the various forms in which it is employed in the arts and in scientific research is very limited. To arrive at satisfactory conclusions, the experiments on this material were extended so as to embrace the direct tenacity, the resistance to compression, and the resistance to bursting, as well as the resistance to collapse.

The glass experimented upon was of three kinds.

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Flint-glass.. Green glass Crown-glass

Mean resistance to crushing. in pounds. in tons. 13,130... 6.861 20,206 9.010 21,867 9.762

Hence, comparing the results on cylinders with those on cubes, we find a mean superiority in the Former case in the ratio of 1.6: 1, due to the more perfect annealing of the glass.

ON THE RESISTANCE OF GLASS GLOBES TO INTERNAL PRESSURE.

In these experiments the tenacity of glass is obtained by a method free from the objections to that before detailed. Glass globes, easily obtained of the requisite sizes, in a nearly sperical form, were subjected to an internal pressure obtained by increased till the globe gave way. means of a hydraulic pump, uniformly and steadily The lines of fracture radiated in every direction from the weakest part, passing round the globe as meridians of longitude and splitting it up into thin bands, varying from th to th of an inch in breadth.

The following table gives the results of the experiments on the resistance of glass globes to internal pressure :—

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rupture or line of minimum strength; A= the longitudinal sectional area of the globe in square inches; and T=the tenacity of the glass in pounds per square inch. Hence, from the above experi ments we deduce:

Pounds.

T=4200 for flint-glass, = 4800 for green glass, =6000 for crown-glass,

5000=mean tenacity of glass. Here the mean tenacity is nearly twice that obtained in the experiments upon thick bars; a result which, perhaps, corresponds with the difference between the crushing strength of cylinders and cubes, and is largely attributable to the condition of annealing.

ON THE RESISTANCE OF GLASS GLOBES AND CYLINDERS TO AN EXTERNAL PRESSURE,

The manner of conducting these experiments did not differ in any essential detail from that pursued in the experiments upon wrought iron. The globes and cylinders, after having been hermetically scaled in the blowpipe flame, were fixed in a wrought-iron boiler communicating with a hydraulic pump. In this position an increasing pressure was applied until the globes broke, the amount of pressure at the time being noted by means of a Schäffer pressure-gauge. During the collapse the globes were reduced to the smallest fragments, so that no indication of the direction of the primary lines of fracture could be discovered.

The following table contains a summary of the results on globes subjected to an external pres

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The paper includes an investigation of the laws of collapse in these results, and the following general formulæ are obtained :

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For glass globes

4.5 by 4:55

0.036

280

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60 by 6:3 The formula which expresses the relation of the bursting pressure to the thickness and diameter of the globe, is:

aT P=; A

The experiments in this section were made upon small cylinders and cubes of glass crushed between parallel steel surfaces by means of a lever. cylinders were cut of the required length from where a the longitudinal sectional area of the rods drawn to the required diameter, when molten, material in square inches, that is, in the line of

=

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D.L where P the collapsing pressure in pounds per square inch; thickness in inches; D) and L= diameter and length respectively in inches.

These are the general formula for glass vessels subjected to an external pressure, and the latter is precisely similar to that found for sheet-iron cylinders.

TRANVERSE STRENGTH OF GLASS.

The authors derive the general formula
K.D
W=3140 x

where W = breaking weight in pounds, K = area of

These globes remained unbroken. + Remained unbroken.

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