yielding easily to the hammer, bearing distortion well, and flattening in two or three directions without cracking. It seemed to be sensibly less hardened by hammering than the ordinary metal of commerce.

'Chemical News,' 1859: M. Degousse has succeeded in beating aluminium into leaves as thin as those obtained of gold or silver. The operation is attended with a certain difficulty, and it is necessary to temper the metal frequently. This cannot be done, however, in the ordinary manner as with gold or silver; only a very slight heat must be employed. The beating is done as usual. These thin aluminium leaves can be substituted for silver leaf. They have a less brilliant color, but are much more durable, and may be employed advantageously for decorative purposes. A very thin leaf will burn like paper when made into a roll, with a brilliant white flame.

Kerl & Stohman: Aluminium may be rolled as easily as other metals, but it must be annealed oftener. The annealing of objects made of it is not more difficult than that of other metals. The moment the metal begins to glow its annealing is complete. Those metal-workers who are anxious about the exact point of time can rub the top of the article to be annealed with a lump of fat, the disappearance of the fat shows the moment in which the object is to be removed from the annealing oven. Aluminium can also be pressed or

stamped into all forms of hollow and round vessels, in a stamping press. But there must be used a kind of varnish of 4 parts of oil of turpentine and 1 part of stearic acid.

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Bell Bros. Aluminium can be beaten out, hot or cold, to the same extent and as perfectly as gold and silver, and may be rolled in much the same way. Thin leaves may be used in the same manner as gold and silver leaf. Covered iron ingot moulds serve best for casting bars of the metal to be rolled. Aluminium quickly loses its temper, and therefore requires frequent reheating at a dull red heat; when the plates are very thin this demands great attention.

Mierzinski: The extensibility of aluminium is quite high, standing near to gold and silver. It may easily be beaten out or rolled without tearing. In beating to leaf it should at first be warmed only to 100° or 150°, an actual glowing heat has proved to be very unsuitable. Such leaves are especially suitable for showing the characteristic qualities of the metal; for instance, it dissolves with extraordinary quickness in caustic alkali, leaving the iron, which is always present. This leaf is also very combustible, even in a gas flame, burning with a brilliant, sparkling light; the resulting Al2O3 is melted, and as hard as corundum. While water does not appear to be decomposed by aluminium in compact masses at 100°, yet it does so when in the extremely attenuated form of leaf. In pure,

boiling water the leaf slowly evolves hydrogen, after several hours the leaves are half gone, being changed into hydrated alumina. Aluminium leaf was first made by C. Falk & Co., Vienna.

DUCTILITY.

Deville: Aluminium behaves very well at the drawing plate. M. Vangeois obtained in 1855, with a metal far from being pure, wires of extreme tenuity, which were used to make aluminium passementere. However, the metal deteriorates much in the operation, and the threads become flexible again only after an annealing very delicately performed, because of the fineness of the threads and the fusibility of the metal. The heat of the air coming from the top of the chimney over an Argand burner is sufficient to anneal them.

Bell Bros.: Aluminium is easily drawn into wire. Run the metal into an open mould, so as to form a flat bar of about one-half inch section, the edges of which are beaten very regularly with a hammer. The diameter should be very gradually reduced at first, with frequent heating. When the threads are required very fine the heating becomes a very delicate operation, on account of the fineness of the threads and the fusibility of the metal.

ELASTICITY-TENACITY-HARDNESS.

Deville: The elasticity of aluminium, according to M. Wertheim, is sensibly the same as that of silver; its tenacity is also nearly the same. The moment after being cast it has the hardness of virgin silver; when it has been worked it resembles that of soft iron, becomes elastic by becoming much more rigid, and gives the sound of steel when dropped on a hard body.

Mallet: Absolutely pure aluminium was distinctly softer than before purification. Hence its fracture was not easily observed, but seemed to be very fine grained with some appearance of fibrous silkiness. It seemed to be sensibly less hardened by hammering than the ordinary metal of com

merce.

Fremy: Aluminium just cast is scratched by a wire or edge of silver, but by hammering it becomes as hard as iron and elastic. The tenacity of aluminium wire is between that of zinc and tin, but by hammering it attains that of hardened copper. When cast carefully it can be easily filed without fouling the tool.

Kerl & Stohman: Aluminium resists the action of the engraving tool, which slides upon the surface of the metal as upon hard glass. But as soon as one uses the varnish of 4 parts of oil of turpentine and 1 of stearic acid, or some olive oil mixed with rum, the tool cuts into it like pure copper.

Mierzinski: The tenacity of aluminium is very remarkable, and, according to Barlow, is 1892 kilos per square centimetre; the extensibility 2.5 per cent.

W. H. Barlow:* A bar of aluminium three feet long and one-quarter inch square was obtained, and different parts of it subjected to tests for tension, compression, and transverse strain, elasticity, elastic range, and ductility. It will be seen on reference to the results that the weight of a cubic inch was 0.0275 pound, showing a specific gravity of 2.688, and its ultimate tensile strength was about twelve tons per square inch. The range of elasticity is large, the extreme to the yielding point being onetwo hundredth of the length. The modulus of elasticity is 10,000. The ductility in samples two inches long was 2.5 per cent. Taking the tensile strength of the metal in relation to its weight, it shows a high mechanical value. These results are thus tabulated:

It thus appears that taking the strength of aluminium in relation to its weight, it possesses a

* Rpt. Brit. A. A. S., 1882, p. 668.