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ment of the sword. And hence we are content to see, in the midst of the peaceful gathering of the works of our industry and our art, the most perfect finish, the most subtle invention, and the utmost resources of our mechanical skill expended on the “ works of war."

How to arm our navy to resist the heavy projectiles of modern artillery, and, above all, how to keep out those frightful instruments of destruction, the explosive and molten iron shells, is a problem involving conditions so novel that, during the past year, it has raised more discussion amongst engineers than any other. In the pamphlet before us, Mr. Fairbairn contributes the results of his experience and research, as to the qualities of iron, and the mode of its application best adapted for the protection of ships of war. He long since expressed the opinion that the material, which has almost superseded wood in the mercantile marine, would ultimately prove most suitable for the navy; and this, notwithstanding the adverse results of the partial experiments in 1827, and subsequently. He has lived to see his opinion universally shared, and satisfactorily established in actual warfare, at Kinburn in 1855, and more recently in America. In the new conditions in which we are thus placed, by the improvement of artillery on the one hand, and by the adoption, by other nations, of iron armour for purposes of defence, after satisfactory proof of its superiority to wood,

“We must look,” says Mr. Fairbairn, “to new materials, and an entirely new construction, if we are to retain our superiority as mistress of the seas. There yet remain amongst us those who contend for wooden walls, but they are no longer applicable to the wants of the State ; and I am clearly of opinion, that we cannot afford to trifle with so important a branch of the public service as to fall behind any nation, however powerful and efficient they may be, in naval construction,”

He adds, that a revolution is in progress in the destiny of the navy, and then continues :

" It is not for us alone that cyclopean monsters are now issuing from the furnaces of Vulcan; and it behoves all those exposed to such merciless enemies to be upon their guard, and to have their Warriors, Merrimacs, and Monitors ever ready, clothed in mail from stem to stern, to encounter such formidable foes. It has been seen, and every experiment exemplifies the fact, that the iron ship, with its coat of armour, is a totally different construction to the wooden walls which for centuries have been the pride and glory of the country. Three-deckers, like the Victory and the Ville de Paris of the last century, would not exist an hour against the seamonsters now coming into use. The days of our wooden walls are therefore gone; and, instead of the gallant bearing of a 100-gun ship, with every inch of canvas set, dashing the spray from her bows, and careering merrily across the ocean, we shall find in its place a black demon, some five or six hundred feet long, with a black funnel and flagstaff, stealing along on her mission of destruction, seen above water sufficiently only to exhibit a row of teeth, one on each side, as formidable as the immense iron carcase floating below. This may, with our present impressions, be considered a perspective of the future navy of England ; probably not encouraging, but one on which the security of the country may ultimately have to depend, and to the construction of which the whole power and skill of the nation should be directed.”

In reading this description of the unromantic attributes of a modern mail-clad vessel, some of our readers will probably deplore the entire disappearance of the poetry, hitherto associated with the navy, and may perhaps be reminded of Byron's lines :

“She walks the waters like a thing of life,
And seems to dare the elements to strife.
Who would not brave the battle fire,-the wreck,
To move the monarch of her peopled deck!”

and then turn somewhat deprecatingly to that most graphic account of the Monitor as “a Yankee cheese-box on a raft,” which is said to give a better idea of her appearance than any of the engravings which have been published. In our own armour-clad vessels, the æsthetic element has not hitherto been sacrificed to so great an extent; but Captain Coles's cupola ships which are in progress will closely accord with the American type.

The questions dealt with in the pamphlet relate to the quality of iron most suitable for armour-plates, and the laws of resistance of such plates to projectiles, as determining the conditions under which they should be applied in naval construction.

Of the three materials, cast iron, wrought iron, and steel, the first is manifestly defective in all the qualities requisite; but the choice between the other two is more difficult. Tenacity, or cohesive force and toughness, or capability of yielding to a blow without fracture, are pointed out as the qualities most desirable. The tenacity of steel is twice as great as that of wrought iron; but Mr. Fairbairn implies that in the trials with ordnance it has proved inferior, even when so soft as to contain only 0.25 per cent. of carbon. If this be the case, our French rivals have made a mistake in clothing La Gloire with steel-faced plates.

It is interesting to remark, that chemistry has aided the engineer in this inquiry, the absence of carbon being one of the most available indications of the value of an armour-plate. The data which Mr. Fairbairn quotes show also that the most minute excess in the proportions of sulphur, phosphorus, and silicon, in Dr. Percy's analyses, correspond exactly with deteriorations of strength in his own experiments on the same plates, and with inferiority in resistance to projectiles in the trials at Shoeburyness. The purer the iron, therefore, the greater its value for defence. This result might have been anticipated, but it is none the less interesting to find it clearly demonstrated in independent researches.

In defensive constructions the engineer has to comply with entirely new laws of resistance. Hitherto he has almost universally dealt with slowlyapplied forces, which it was convenient to regard as dead (or statical) pressure. But projectiles have a velocity of 1,100 to 2,000 feet per second, and inflict an injury wholly incommensurable with the statical resistance of the plates. Statical forces acting for an indefinite period are regulated by one law; sudden and almost instantaneous impact, by an entirely different one. It is in consequence of a misconception on this point that much of the discrepancy of opinion on the subject of iron armour has arisen. And an adequate return will have been made to engineers for the service they have rendered to naval construction if it induces them to pay more attention to the dynamic resistance of materials. It will lead to the explanation of many catastrophes (boiler explosions and the fracture of the Hartley Colliery beam, for example) which have been considered almost inexplicable. And war will thus have nourished the arts anew, and yielded fruits of peace.

Mr. Fairbairn shows that the destructive power of the shot depends on its ris viva, or the work accumulated in it during the explosion of the powder, and which is known to vary as the product of the weight of the shot and the square of the velocity generated. This product is in turn

therefore, merely a carrier of the energy disengaged by the chemical decomposition of the powder. That the destructive power of the shot increases with the square of the velocity explains the inefficiency of the American

can be expended as compared with the guns employed in the experiments in this country. It also explains the enormous power of the 300-pounder smooth-bore at Shoeburyness when firing a 150-pounder ball with a charge of 50 lb. of powder. Of this last Mr. Fairbairn says :

“We had just arrived at the desired point of security when the thundering 300-pounder, smooth bore, upset our calculations and levelled the whole fabric with the ground.'

The velocity of the 150 lb. shot probably approached 2,000 feet per second.

On the vexed subject of “ships versus forts” Mr. Fairbairn sides with Lord Palmerston. He says :

“A great outcry has been raised about the inutility of forts; and the Government, in compliance with the general wish, has suspended those at Spithead; I think improperly so, as the recent experiments clearly demonstrate that no vessel, however well protected by armour-plates, could resist the effects of such powerful artillery” (as the 300-pounder alluded to above).

Whether the doubt, expressed in the last paragraph, as to the possibility of obtaining invulnerability in ships is well founded must be determined by further experiments ; but, looking to the law enunciated by Mr. Fairbairn, that the resistance of plates increases as the square of the thickness, it would appear that at present our means of defence in ships are in advance of the artillery which can be brought to bear against them. The enormous 300-pounder only just penetrated the target representing a section of the Warrior and protected by 4-inch plates, and that, too, after it had been struck by 3,229 lb. weight of metal. But 5 and 51 inch plates are being employed, which will increase the resisting power by 25 and 50 per cent, respectively, and it is doubtful whether these would be penetrated by even the most powerful modern artillery, at least with the present cast-iron service-shot. In America, 104-inch plates have been used, but there is no doubt, a limit to the thickness to which the law of the squares applies. Very thick plates of wrought-iron have been found to break brittle like plates of steel, either from a deterioration in the quality of the material or from the rigidity of a thick mass, causing fracture according to a different law. The entire invulnerability of the

American iron-cased vessels in actual warfare, imperfectly as they are constructed when compared with the Warrior or Black Prince, is very remarkable. Whilst, on the other hand, the terrible effect of shells on the wooden Cumberland, in the battle of Hampton Roads, which, in a short half hour, made her interior look like a burnt and sacked house” and sent her blazing to her ruin, may teach us that, whether absolute invulnerability is attainable or not, it is a prime necessity of modern warfare, and a guarantee for peace, to provide such security as iron will afford against these new missiles.

A Glossary of Mineralogy. By HENRY WILLIAM Bristow, F.G.S.

Longman, London. 1862.

M INERALOGY is a science that has few votaries in England, but a MI certain knowledge of it is indispensable to the chemist and geologist; and to these the book lately published by Mr. Bristow will be found extremely useful, if not indispensable, for reference.

Mr. Bristow does not confine himself to a mere alphabetical descriptive list. In a short introduction he notices the various properties of minerals and the modes of determining them. Like other geologists who have to use this science as an adjunct, he leans to a chemical arrangement, quoting the method followed by Professor Warrington Smyth at the Museum of Economic Geology, which in all essential features resembles that adopted by Professor Ansted in his Elementary Course of Geology and Mineralogy. He introduces a very large number of synonyms; and the accounts of the principal minerals are pithy, definite, and comprehensive. Remarkable specimens in the public museums of England are referred to, and localities are not neglected. The composition is quoted either by chemical symbols or as a distinct analysis.

In the present state of mineralogical science and it is not likely soon to improve-there is a great advantage in the alphabetical arrangement, as those who have consulted the works of Dana and even of Phillips, in its most approved form, will generally admit; and we doubt not that Mr. Bristow's book will be useful. We would suggest, however, that in a future edition he should give a few more cross references, and bring down his list of localities to accord with recent discoveries. It is rather puzzling to have to think under what heading sulphur, silver, and copper are to be sought, and not easy to see why gold should be described under its own name and the other minerals we have mentioned as natives. We miss, too, names so common as Kaolin, finding Pe-tun-tse and Kunkur, which are much less defined varieties. We miss also Lederolite (a variety of Chabasite); Marmatite (a variety of Blende), and a few others. These are pointed out rather to show that a careful revision is desirable, than as finding fault with a task which, on the whole, is very well accomplished.

On the various Contrivances by which British and Foreign Orchids are

Fertilized by Insects, dc. By Cuas. Darwin, M.A. (Illustrated.)

Murray. M HE perusal of Mr. Darwin's book on “ The various Contrivances by

1 which British and Foreign Orchids are fertilized by Insects," might incline the reader to regard it as the result of nothing less than a life devoted exclusively to the subject. Yet of the great discussion concerning the “ origin of species,” the present work is, in fact, only a single chapter, the details of which have become inconveniently large to be incorporated with the rest of the argument.

The point which the author here seeks to establish is thus stated. “That nature abhors perpetual self-fertilization.” “That marriage between near relations is in some way injurious—and that some unknown great good is derived from the union of individuals which have been kept distinct for many generations."

Self-fertilization is a rare event with the Orchids, and the description of the various contrivances by which the pollen of one plant is kept from contact with its own stigma and conveyed to that of another plant of the same species, occupies nearly the whole of the volume.

Orchids, it appears, are favourite plants with honey-loving insects. When the proboscis of a bee or a moth is inserted into the nectary of an orchid, it first comes in contact with a little capsule or pouch, the membrane of which at the slightest touch is ruptured, setting free a liquid and exposing the sticky ends of two club-shaped organs, to the further ends of which the pollen grains are attached. The sticky ends instantly adhere to the proboscis, which, when retracted, carries with it the pollen clubs fastened upon it in a somewhat erect position. Further down the throat of the nectary lies the stigma.

We have then to observe (first), the retired position of the anther chambers, of which there are two, containing the charged ends of the pollen clubs. (Second.) The prominent position of the viscid ends of the pollen-clubs in the throat of the nectary. (Third.) The manner in which the sticky ends of the pollen-clubs are kept moist, till wanted for use, by being immersed in a little pouch of liquid. (Fourth.) The extreme sensitiveness of the lips of this pouch, which open at the slightest touch imaginable. (Fifth.) The rapid setting of the viscid matter, which hardens into a dry cement in a very short time after the sticky ends of the pollen-clubs have touched the proboscis of an insect. (Sixth.) If tlie attached clubs remained erect, the proboscis at its next insertion into a flower would press the pollen grains into a position similar to that from which they had been taken, namely, into the anther chambers; but no sooner are the clubs fast than their pedicels uniformly begin to curl forward, bringing the pollenized ends of the clubs almost close to the prohoscis in a more forward position, so that when the next flower is visited the proboscis pushes the pollenized tips of the clubs past the anther chambers and right upon the stigma of the flower.

In the genus Catasetum the flower has two slender horns, which when

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