THE FUTURE OF ALUMINIUM. T HE elegant winged figure with which
Mr. Gilbert has adorned the summit of the bronze fountain designed and cast by him for the centre of Piccadilly Circus, possesses an interest separate and apart from its merits as a work of art. The statue, which was originally intended to be cast in bronze, is made of pure aluminium, and the brightness and beauty of the material, which has all the appearance of frosted silver, together with a suggestion of lightness quite peculiar to this new and exquisite metal, must be apparent to the least obser- vant passer-by. Its employment in such an important piece of outdoor decoration in London cannot fail to draw attention to what, among those who are at all beforehand with the world in the pursuit of practical science, is among the most eagerly discussed questions of the day,—the probable future of alu- minium. Even apart from its material uses, there is enough in the nature and history of the metal itself to make it a sub- ject more than usually attractive to the imagination. Its very existence is an example of the possibility of the inconceivable. As we know, it does not exist in Nature in any form per- ceptible by the senses. There is no such thing as an alumi- nium nugget or aluminium dust. It cannot be crushed out or washed out, or even burnt out of the earth, except with the aid of the electric furnace at a temperature of 6,000° Fahrenheit; yet it is present in every load of London clay, and wherever else clay-beds lie it exists potentially in quantities and over areas to which even the coal-measures cannot be compared either for richness or extent. When once obtained from the clay, its peculiar properties are more obvious and striking than those of any other material. It is beautiful to the eye, whiter than silver, and indestructible by contact with the air. It neither rusts nor tarnishes ; is strong, elastic, and so light that the imagination almost refuses to conceive it as a metal, the connection between heaviness and strength being almost as firmly established in most minds as that between heaviness and warmth, and refusing to admit any comparison between the comfort afforded by an eiderdown or a sheepskin; the weight is little more than one-third of the corresponding bulk of iron, and of course far less than that in the proportionate amount of silver, gold, or lead.
The so-called "aluminium gold" of which watch-chains and trinkets were commonly made some years ago, is merely an alloy of copper containing a small per-tentage of aluminium, which gave to the copper brightness and hardness, with abso- lute freedom from tarnish. " Aluminium bronze," the materia of which the Austrian field-guns are constructed, also contains only some 6 per cent. of aluminium, though the material so produced is of extreme hardness and value for the purposes for which it is used. But the value of pure aluminium—light, strong, non-corroding, lustrous and beautiful to the eye, in- offensive to the senses of taste and smell, and so malleable that (like gold) it can be beaten-out into thin foil or drawn into fine wire—is such as to offer an inducement to the dis- covery of a cheap and simple method of extracting the bound- less store in the clay-beds of the world, hardly exUeeded by the desire to discover the philosopher's-stone itself. Nowhere, indeed, does the old fancy of the transmutation of metals come nearer an apparent realisation than in the change from masses of shapeless clay into white and shining blocks of silvery aluminium. Even now, with the existing methods of elaborate chemical treatment, or the intense heat of the electrical furnace, pure aluminium can be bought for 2s, per pound in Germany, and at 28.6d. per pound in England. Good gun-metal —not the rubbish which is sold as "brass "for door-knobs and curtain-poles, and other household fittings—costs Od. per pound. But as the quantity of aluminium represented by a pound- weight is three times that of an equal weight of copper, the cost of the aluminium, bulk for bulk, is in the proportion of 9d. to that of 6d. for the copper. Compared with the so-called brass, it is already equally cheap and equally strong, with far greater lightness and beauty.
The present cost of aluminium, though still higher than any of the cheap metals, has brought it within the range of everyday life; and its present uses, limited as they are, necessarily bear some relation to the great question o£ th f the future of the new metal, and the possibility of realising hopes of the metal-worker and the engineer. For all personal equipment which must be carried by the owner, aluminium is rapidly taking the place of every other metal. Its light- ness is its obvious recommendation in this case. In the German cavalry, even the stirrup " irons " are now made of aluminium. The men's water-bottles are also of the same light and strong material. In binoculars for field use, and all kinds of scientific instruments for distant and toil- some expeditions, such as Dr. Nansen's Arctic journeys, or observations on high mountains, the same metal takes the place of the heavier brass, when the saving in weight so secured may often make the difference between scientific success or failure. Nearly all the small articles of luxury and ornament usually made in silver or brass are now produced in aluminium, though where weight is not a drawback, the gain is rather one in appearance than in construction. But aluminium thimbles, penholders. paper-knives, flasks, or cups are so far superior to those made of the ordinary materials, that no one who has once made use of them in the new metal will readily return to the older form. A far more important and significant step is the recent construction of large aluminium launches on the Lake of Geneva, and of the aluminium house at the World's Fair at Chicago. In the first case, the object proposed was double,—the gain of nearly two-thirds in lightness in the hull, which, in the case of a pleasure-boat with small engines, would naturally result in a greater comparative gain of efficiency than in the enormously over-engined torpedo-boat or fast cruiser, and a reduction of the surface-friction by the use of a smooth, polished, and non-corrosive material. Both these results are said to have been obtained, though the great preponderance in cost of the aluminium even over the best steel, renders its use for such purposes at present beyond the sphere of practical commerce. The aluminium house, also, should contain the elements of constructive success. So light and tough a material is better suited for the construction of a moveable home than any other. Moreover, aluminium, which itself possesses a high degree of specific heat, does not readily absorb heat itself, and thus is not liable to the chief objection to iron buildings in hot countries. But apart from light decorative purposes, such as balconies, cupolas, finials, and verandahs, it is as a roofing material that aluminium should be most welcome to the builder. In plates or scales, two-thirds lighter than copper, uncorroded by air, and un- dimmed even by the sulphur of London smoke, it should make a roof fit for a palace of romance. The humbler elements of health and comfort in the house hardly less important than its external defences against the weather—pipes, cisterns, taps, and gutters, now made of iron which rusts, or lead which poisons—would be more enduring and far more healthy if made of this light and cleanly metal, which might also take the place of all water-holding vessels now made of heavy brittle earthenware, or painted tin. An aluminium bath is among the probable luxuries of the next century. But it is not as a mere accessory to comfort and convenience that real development of the new metal should lie. It is for use at sea that its most marked quality of lightness obviously fits it. The marine engineer, and the naval archi- tect, who are already looking in this direction for a reduction in the weight which is inseparable from loss of efficiency, whether in speed or cargo, cannot neglect the possibilities of a metal which, when mixed in the proportion of 1 to 50, gives to aluminium-bronze a hardness and toughness which make it almost as reliable as steel, and which, if the propor- tions could be reversed, and the strength preserved, would reduce the weights of ships and machinery alike by two-thirds. That is a problem which awaits the metal- lurgists for solution. The reduction in cost, judging by analogy, can only be a question of time and research. The best steel now oosts little more than Id. per pound ; while aluminium is fifty times that price. But aluminium exists in far greater quantities than iron, is more widely distributed, and neither the limits of time nor the history of metallurgy forbid us to conjecture that, as the world has seen its age of atone, its age of bronze, and its age of iron, so it may before long have embarked on a new and even more prosperous era, —the age of aluminium.