we have briefly to notice some of the improvements and changes that have taken place in the construction of ordnance and the art of defence, and to chronicle some of the most important results which have placed the whole of our naval and military armaments in a state of transition. It is now well understood that His Majesty the Emperor of the French was the first to apply iron plates as a defence to the sides of ships, and that ships of war protected with a given thickness of plate 4 inches were invulnerable to shot or shell. For a considerable length of time this opinion was prevalent, and was acted upon both in this country, France, and America. The experiments instituted by the Admiralty and War Office have, to a great extent, dispelled these notions; and it has been proved that a smooth-bored Armstrong gun, with a 150-lb.spherical shot, can pierce a43-inch-thick plate and 18inches of teak. In fact, it has been proved by experiment that no vessel yet constructed is able to carry armour-plates of sufficient thickness to resist such powerful ordnance as has been brought against them.

Every effort has been made on the part of the Government to determine experimentally the properties of iron best calculated to resist shot, and the greatest possible care has been observed, both in a chemical and mechanical point of view, to secure the very best description of iron for that purpose. All these facts have been ascertained, as also the penetrating powers of different descriptions of ordnance as compared with the thickness of the plates to be pierced. In this position the balance of force to the resistance of the plate was in favour of the gun, but with this qualification, that the gun had to sustain an explosive force of powder equivalent to one-third the weight of the shot, a charge which the gun was unable to bear. Under ordinary circumstances, with the usual charge of one-eighth the weight of the shot, it might reasonably be inferred that the balance was on the side of the plate, and that guns of such heavy calibre were insufficient in strength to sustain these tremendous charges of powder. Again, it must be borne in mind that these results were only produced at certain distances, and under certain conditions of heavy charges of powder and a short range of 200 yards.

The inquiry was thus hanging on the balance, when it was determined to ascer→ tain the effect of the large Horsfall gun of 22 tons weight with a charge of 75 lbs. of powder and a 300-lb. shot, against a target representing the 'Warrior,' with her 18 inches of teak and 4 inches of iron. The result of this experiment was the penetration of the mass, with a huge opening in the side of the target upwards of 2 feet in diameter. This experiment is probably not calculated to apply to ships of war carrying ordnance of such immense weight, but it is greatly in favour of forts, where an enemy's vessel may be struck at a distance of 1000 yards.

Passing from the Horsfall gun, we now come to the last and most important experiments with the Whitworth gun: the first was a 12-pounder field-gun, and the second a 70-pounder naval gun; both of the guns were rifled. These experiments are very instructive, and I probably could not do better than quote from the 'Times,' of September 18th, a statement of the effect produced by these guns:-"It will, perhaps, be remembered that a decided difference was established very early in the controversy between the penetrating powers of solid shot and those of shell. Solid shot at one time failed, and at another time succeeded, against armour-plates, according to the modified conditions of the experiments; but shells failed absolutely and invariably. No shell could ever be driven through even a moderately thick plate of iron, and it was concluded, therefore, that this, the most dangerous and dreaded species of missile, could undoubtedly be kept out of a ship by a thin casing of armour.

"Accordingly, as a reduction of a ship's armour to the least possible weight was of great consequence, especially in small vessels, gunboats and other craft of the like description have been built in some countries with 23-inch or 2-inch armour-plates, and considered effectually shell-proof. On Tuesday, however, Mr. Whitworth entered the field with two of his pieces, for the service of which he had specially prepared some flat-fronted, hardened shells. The 12-pounder, at 200 yards, presently sent these shells through a 2-inch plate backed by a foot of timber; from which simple piece of evidence the conclusion is inevitable, that vessels protected to that extent only are shell-proof no longer.

"But in the trial of the 70-pounder an additional result was obtained. It has

been suggested that if, instead of employing a given thickness of iron in one solid piece, the armour of a ship were divided into two plates, each of half that thickness, and these plates were separated by a certain space from each other, the resisting power of the structure might be much increased. The theory was that the first plate, though it would doubtless be pierced, would so deaden the force of the shot, that the second plate would repel it; and, indeed, as regards solid shot, the question remains still undecided. With respect to shell, however, or rather Mr. Whitworth's shells, we are not left in doubt even on this point. The 70-pounder was trained against a target constructed on this principle of a double side. A strong oak frame, armed with 4-inch plates, was attached to a second plated to the depth of 2 inches, an interval of two or three feet being left between them. The shell from this gun, fired with 12 lbs. of powder only, pierced the outer side of the target completely, oak and iron together, after which it burst inside the frame and shattered it to pieces."

From this statement we learn, that 4 inches of solid iron and 9 inches of wood are no protection against shells discharged from a moderately sized gun, and that no gunboat, such as those on the American waters, could prevent the entrance of these dreaded and destructive missiles. In point of fact, Mr. Whitworth, with a rifled gun lighter than the 68-pounder, could destroy them by his steel-hardened shells at a distance of 1500 to 2000 yards.

Since the above was written another experiment has been made with a still larger gun, rifled on Mr. Whitworth's hexagonal principle. This gun was of large calibre, 120-pounder, at a distance of 600 yards, and the results seem to prove that the side of a vessel like the Warrior' is no longer shell-proof. In these experiments 130-lb. solid shot, with a charge of 23 lbs. of powder, went right through the 43inch armour-plate and lodged in the teak backing behind. A shell of the same weight, and a charge of 25 lbs. of powder, also penetrated the armour-plate and exploded, tearing the wood backing, and lodged on the opposite side.

From these more recent experiments we may infer that the victory is on the side of the gun, and that it may be difficult, under such fearful odds, to construct ships of sufficient power to prevent their destruction by the entrance of shells. Other experiments are, however, in progress, and means may yet be adopted to solve the question of armour-ships versus shot and shell.

On the Importance of Economizing Fuel in Iron-plated Ships. By E. E. ALLEN. Iron-plated ships, to be efficient, ought to be able to carry coals for fourteen days; but in consequence of the weight of the armour, and the present mode of generating and using the steam, only coals enough for seven days can be carried. In future wars, despatch in going to the seat of war, and high speed in manoeuvring, will be necessary; therefore much fuel must be used; hence the desirability of studying how to economize fuel. The deficiency of boiler-power in the Royal Navy is too well known. Modern inventions have increased the displacement of ships: thus, the armour, coals, and machinery are about equal in weight; and 1000 horses' power will consume 200 tons of coal a day, under full steam, say at ten knots per hour; but the necessary power for increasing the speed from ten to twelve knots demands double the fuel; and if the speed be increased to sixteen knots, the amount of fuel must be quadrupled. Some of our new war-ships only move at 93 knots an hour, whereas it is generally allowed they should make 15 knots; 5000 miles ought to be steamed without re-coaling, but only one-third of that distance can be accomplished. As a proof that the boilers are too small, it may be affirmed that none of the ships in the Royal Navy can work full steam, and keep the throttle-valves open, for more than a few hours at a time. Six-hundred horse-power boilers should be used where only 400 horse-power boilers are now used. Coal is the only item in which weight can be saved. The merchant vessels only consume half the coals (for ships of the same size) of those in the Royal Navy. Cornish engines consume 2 pounds of coal per horse-power per hour; 2 pounds ought to be the limit in marine engines; but 6 pounds are generally used in the Royal Navy. He proposed the following methods for economizing fuel:-To proportion the boilers to the steam required; to increase the capacity of the cylinders, but not the length of the stroke;

to superheat the steam; to jacket the cylinders to warm the injection water; to work the steam expansively by having two cylinders, a small one at the back of the large one, or concentrically within the large one, and to let the steam into the small cylinder first. Although he recommended this to our Admiralty in 1855, no notice was taken of it. The Swedish Government have adopted it in their new gun-boats, and it obtained a medal at the present Exhibition. By these arrangements for economy, and with better-designed engines, 17,000 tons of coal per day might be saved throughout our fleet; but now, after steaming 2000 miles, the ships have to creep into port, under canvas, to be re-coaled. 40 per cent. of power might be added, and therefore a greater speed of one-and-a-half knot per hour obtained, without greater displacement; and 14 tons per horse-power per annum, or a million tons of coals per annum, for the whole fleet might be saved.

On Artificial Stones. By Professor D. T. ANSTED, M.A.

In this paper the author described the various materials and contrivances used for the purpose of replacing stone where natural stone could not be advantageously procured. He described, in succession, terra cottas, cements, and siliceous stones, pointing out the character, properties, uses, advantages, and disadvantages of each. He alluded to experiments made in the laboratory on the various methods suggested for preserving stone by a Section of the Committee recently appointed by the Board of Works in reference to the Palace of Westminster; Dr. Hofmann, Dr. Frankland, Mr. Abel, and the author being members of it. During their investigations a remarkable material was submitted by Mr. Ransome for their consideration, and its discovery arose out of Ransome's method of preserving stone by effecting a deposit of silicate of lime within the substances of the absorbent stone, saturating the surface with a solution of silicate of soda, and then applying a solution of chloride of calcium; thus producing a rapid double decomposition, leaving an insoluble silicate of lime within the stone, and a soluble chloride of sodium, which could afterwards be removed by washing. To prove this, Mr. Ransome made small blocks of sand in moulds by means of silicate of soda, and then dipped them in chloride of calcium. The result was the formation, almost instantaneously, of a perfectly compact, hard, and, to all appearance, a perfectly durable solid. Mr. Ransome at once adopted the process for the formation of an artificial stone which, the author of the paper considered, would combine the advantages, and avoid some of the disadvantages, of other artificial stones. Experience, however, can alone be the test of its durability. A specimen weighing two tons was shown in the International Exhibition, and the substance is used in the stations of the Metropolitan Railway. It is cheap, and can be made, on the spot, of almost any rubbish or material, and of any form or size. Experiments made by Mr. Ransome show that, as compared with Portland stone or Caen stone, a bar with section 4 inches square and 8 inches long, suspended midway between supports, sustained 2122 lbs., while similar bars of Portland and Caen stone broke respectively with 750 lbs. and 780 lbs. The adhesion of the stone was shown by weights suspended from a piece prepared to expose a sectional area of 5 inches. Caen stone separated at 768 lbs.; Bath, at 796 lbs.; Portland, at 1104 lbs.; Elland Edge, at 1874 16s.; Ransome's, at 1980 lbs. A cube of 4 inches of Ransome's stone sustained 30 tons.

Unsinkable Ships.

By CHARLES ATHERTON, late Chief Engineer in H.M. Dockyard, Woolwich. The author observes that competitive rivalry in the construction of ships of war with a view to their being "invulnerable," and in the construction of ordnance with a view to its being effective for penetrating the build even of armoured ships, appears, from the experiments which have been carried on at Shoeburyness, to be a question involving unlimited expenditure in possibly abortive ship-building, the result of which rivalry between ordnance and iron plating, being dependent on future invention, does not admit of present definite solution.

Nevertheless the principle of "invulnerability" in the construction of ships of war by the agency of iron plating having been originated and adopted by France

present the most effective system of naval construction, though admitted

to be imperfect, there has arisen internationally a necessity for its adoption until it shall be met or superseded by some other device; and the object of the author, by this paper, is to bring before the notice of the British Association for the Advancement of Science the question, which has been otherwise publicly agitated by him, whether the principle of "invulnerability," as based on "armour-plating," may not be superseded by the principle of "unsinkability," as based on the principle of constructing ships with such a mass of uninflammable materials of a specific gravity less than that of water as shall support the hull and its entire load, and float, however perforated by shot laterally through the sides of the ship, or vertically through the deck and bottom of the vessel by the still more formidable effect of an improved mortar-practice pitching shells of great weight with an infallible precision at short range, or even still float in parts when severed by the concussion of a hostile ram.

Though the vessel may thus be "unsinkable," it is not professed or anticipated by the author that war would be prosecuted without the sacrifice of blood; for though the proposed construction of shipping would be well adapted for protecting the crews of ships from small arms, still the cannon or the mortar would take effect. The chief point on which the principle of "unsinkable ships" is put forward by the author as claiming consideration is that, by the adoption of this principle, the whole crew of a ship would not be simultaneously drowned through the effective application of a single shot, shell, or ram-stroke, as might be the case with armoured ships, seeing that the direct fire of artillery is still paramount, and the mortar practice above referred to has not yet been tried.

A further advantage consequent on adopting the principle of "unsinkability would be that it does not necessitate the construction of ships of such large size as is required for carrying out the principle of "invulnerability" by armour-plating. Also by avoiding top-weight, by which armour-plated ships are so much encumbered, many difficulties in the prosecution of naval architecture are obviated. It is therefore conceived that this principle of "unsinkability" would be well adapted for gun-boats and mortar-vessels destined to act in cooperation with each other in assailing larger vessels at close quarters, or doing service in shoal waters, such Vessels receiving their stores from high-speed steamers of ordinary build acting as store and hospital and barrack ships, to be kept out of harm's way. Also the principle of unsinkability would be well adapted for troop ships and the safe conveyance of valuable cargoes and treasure.

The details of construction of the "unsinkable ship," as respects the disposal of its unsinkable materials, will be dependent on the purpose for which the ship may be especially intended. For example, the whole mass of material on which the ship depends for its unsinkability may be in a solid mass, with the whole of its hold accommodation above the deep-draught water-level; or the vessel may have a hold below the level of the load water-line, provided that the required mass of buoyant material be otherwise disposed of, constituting the sides or ends and bottom and decks of the vessel. Of course such a vessel with a hold below the load-line level may become water-logged, and, if a steamer, disabled; but still such a vessel would sail, and the crew would be alive to do good service from her deck; at all events, her whole crew could not be simultaneously sent to the bottom, which is the great catastrophe intended to be obviated by the principle of unsinkable ships-a catastrophe to which armour-plated ships, though bulkheaded, will be liable if artillery or mortar practice become paramount.

The required brevity of this abstract does not admit of the details of calculation and of construction for the production of "unsinkable ships" of given capabilities being here entered upon; such an exposition, to be complete, would be elaborate, and may engage the future attention of the author.

On Coryton's Vertical-Wave-Line Ships, Self-Reefing Sails, and Guide-Propeller. By JOHN CORYTON, of Lincoln's Inn, Barrister-at-Law. The object of the inventor has been to produce a form of vessel which shall combine the weatherly qualities of a clipper ship, with the advantages of increased speed when going free, and greater safety when scudding before à gale, riding at an

anchor, or becoming suddenly unmanageable through loss of masts, damage to her machinery, &c.

This object is attained by a revolution in the tactics of sailing, as well as in a change of form. When close-hauled, or steaming head to wind, the vessel goesto use the parlance applicable to the present form of ships-head foremost; when sailing or steaming off the wind, she goes, so to speak, stern foremost. In still water the vessel proceeds always on the latter plan. The terms stem, bow, and stern being obviously unsuited to vessels of the proposed form, the inventor substitutes for them the "weather end" and "lee end "respectively.

Novel as the general idea pervading this invention may appear, the deviation in point of form of a Vertical-Wave-Line vessel from the type of ships at present existing is very slight. Taking as a standard a fast clipper schooner of the latest build with a tumble home" bow, fine entry lines, beam carried right aft to the taffrail, and a flat counter, something very like the proposed form will be obtained by cutting away the entire after-keel almost from the fore-foot; the "weather end" thus becoming (approximately) a vertical wedge, and the "lee end" (approximately alse) a horizontal wedge. Provided these forms are preserved, the intermediate work is of little consequence, and may be constructed simply with regard to the ordinary rules of carpentering a point of economy which those practically acquainted with ship-building will not fail to appreciate. "It seems," is the observation of M. Vial de Clairbois in his Architecture Navale' (p. 22), “that naval architects have hitherto affected to avoid straight lines, although geometrically they have the advantage of simplicity over all others." By a coincidence which may appear almost accidental, it will be found that at two points of the vessel constructed on the new principle (and in these, in the larger class of vessels, it is proposed to bulk-head them), sections made by planes slightly out of the perpendicular approach very nearly the catenary-a self-supporting curve. The inventor proposes to construct his vessels of laminated iron up to the water-line, and to make the works above, for the convenience of rough repairs, of wood. By making the iron planks taper towards the ends, and decrease in number as they are placed higher on the ship's side, the greatest strength of the vessel may be placed with almost mathematical accuracy at the point exposed to the greatest strain.

The advantages of this system, besides economy and strength, may be shortly stated thus:-Safety. If disabled, instead of rolling in the trough of the sea like theGreat Eastern on a recent occasion, a Vertical-Wave-Line ship flies head to wind at once, and remains so as long as she can hold together. In boats of this construction "broaching-to" (the fertile source of disaster in passing through surfs or being beached) is entirely avoided, the boat being always kept by the action of the water in the only position compatible with safety. The same peculiarity of form, offering a maximum deflection to an impinging body, renders Vertical-Wave-Line ships admirably adapted for the purposes of naval warfare. A model of a Shield Ship on this principle was exhibited at the International Exhibition during the present year.

Stability.-Vertical-Wave-Line ships will never accumulate rolling motion. From the form of the immersed body, if lateral disturbance take place, the axis of rotation changes with such rapidity as to render it all but impossible that any subsequent impact of wind or sea can have the effect of increasing, and almost certain that each such impact will actually neutralize, the existing momentum. It is this peculiarity, coupled with its safety in exposed situations, that has induced the inventor to suggest this form as suitable for the establishment of a system of Fairway Lighting in the English and Irish Channels, plans and models of which were recently exhibited at the International Exhibition of 1862.

In respect of Speed, a very remarkable phenomenon presents itself, in the case of Vertical-Wave-Line ships sailing off the wind or steaming free, working consequently "lee end" foremost. For every increase of speed there is a decrease of draught. That there is a limit to the truth of this is of course evident; but as a totally new problem, the inventor anticipates from its investigation very extraordinary results. From the absence of keel at the lee end, the vessel steers of course with great handiness, and with the Guide-Propeller can be made to turn in her own length.