or iron contaminating it. The bronze loses by being alloyed with zinc or tin. Second, the alloy must be remelted two or three times to remove its brittleness. In all probability, the percentage of aluminium increases by remelting. The usual alloys are those with 1, 2, 5, and 10 per cent. aluminium. The 5 per cent bronze is golden in color, polishes well, casts beautifully, is very malleable cold or hot, and has great strength, especially after hammering; its defect is that it easily oxidizes or tarnishes. The 7.5 per cent. bronze is to be recommended as superior to the 5 per cent.; it has a peculiar greenish-gold color, which makes it very suitable for decoration. All these good qualities are possessed by the 10 per cent. bronze. It is bright golden, keeps its polish in the air, may be easily engraved, shows an elasticity much greater than steel, and can be soldered with hard solder. It gives good castings of all sizes and runs in sand moulds very uniformly. Thin castings come out very sharp, but if a casting is thin and suddenly thickens, small offshoots must be made at the thick place into which the metal can run and then soak back into the casting as it cools and shrinks, thus avoiding cavities by shrinkage at the thick part.. Its sp. gr. is 7.689, that of soft iron. Its strength, when cast, is between that of iron and steel; but when hammered it is equal to best steel. It may be forged at about the same heat as cast steel, and then hammered until it is almost cold

without breaking or ripping. Tempering makes it soft and malleable. It does not foul a file, and may be easily drawn into wire. Any part of a machine which is usually made of steel can be replaced by this bronze. As a solder for it, Hulot uses an alloy of the usual half-and-half lead-tin solder with 12.5, 25, or 50 per cent of zinc amalgam.”

Fremy: "By the addition of a small amount of copper, aluminium becomes hard, brittle, and takes a bluish-white color. The alloy with 5 per cent. aluminium is very malleable, but if over 10 per cent. Al is present the alloy. cannot be used. The 10 per cent. bronze is now replacing ordinary bronze in the manufacture of articles which are to stand great resistance, such as axle bearings, weavers' shuttles, etc. Reflectors are also made of it, for the smoke of oil, like illuminating gas, does not tarnish it. By whatever method these bronzes are made, they are at first very brittle, but by a series of successive fusions and solidifications they may be made to acquire the necessary solidity and tenacity."

Kerl and Stohman: "Most of the copper-aluminium alloys are very brittle and easily oxidized. Only the 5 to 10 per cent. aluminium alloys are fixed, forgeable, tenacious, and of fine color. Alloys with much aluminium and little copper are not forgeable, and are bluish or grayish-white. With 60 to 70 per cent. aluminium they are very brittle, glass hard, and beautifully crystalline.

With 50 per cent. the alloy is quite soft, but under 30 per cent. of aluminium the hardness returns."

'Chemical News,' vii. p. 220, contains a long paper on testing aluminium bronze (10 per cent.) as to its suitability for the construction of astronomical and philosophical instruments, the work of an English Royal Engineer. He concludes his observations with these words: "It appears from these experiments that the 10 per cent. bronze is far superior, not in one or in some but in every respect, to any metal hitherto used for these instruments. Its sp. gr. is 7.689, strength 73,185 pounds per square inch, to that of gun metal 35,000; it is malleable almost to its melting point, and can be soldered with either brass or silver solder."

'Chemical News,' v. p. 138, contains a number of experiments on the relative strengths of these alloys. The results are as follows, the numbers expressing the results being merely relative :

Bell Bros., Newcastle, give the specific gravity

of the aluminium bronzes as being

'Wagner's Jahresb.' vol. x., contains a long article on aluminium bronze, ten per cent., most of the facts in which have been already given. We may note that the melting-point of this alloy is there stated as about 650°.

Bernard S. Procter,* after describing thirty-one experiments comparing aluminium bronze and brass, sums up the conclusions as follows:

"From the above experiments it appears that aluminium bronze has a little advantage over ordinary brass in power to withstand corrosion, and its surface, when tarnished, is more easily cleaned. This should give it general preference where cost of material is not an important consideration, especially if strength, lightness, and durability are at the same time desirable. It is out of my power to say anything about its fitness for delicate machinery, except that its chemical examination has revealed nothing which can detract from the preference its mechanical superiority should give it. Being so much less acted on by ammonia and coalgas suggests its suitability for chemical scales, weights, scoops, etc. Its resistance to the action of the weather and the ease with which tarnish is removed render it especially applicable for door

* Chem. News, 1861, vol. iv. p. 59.

plates, bell-handles, etc. Its mechanical strength and chemical inactivity together recommend it for hinges exposed to the weather. In experiments 18, 22, etc., the tendency of brass to corrode on the edges and at any roughness on its surface will be observed, while the bronze is free from this defect. In several cases the bronze seemed to be more quickly covered with a slight tarnish which did not increase perceptibly, probably the tarnish acting as a protection to the metal; but the brass, though less rapidly discolored, continued to be corroded and apparently with increased speed as the action was continued. The bronze is more easily cleaned. For culinary vessels its superiority to metals now in use appears questionable. Various philosophical instruments are among the purposes for which the use of the bronze appears advantageous. Undoubtedly, the great obstacle to its extensive application is its high price, resulting partly from the difficulty of getting sufficiently pure copper, the presence of a small amount of iron being very prejudicial." The author states that he wrote the article with a home-made pen of aluminium bronze, and suggests that it is well worthy of the attention of pen-makers.

Thurston says: "The ten per cent. bronze has a tenacity of about 100,000 pounds, compressive strength 130,000 pounds, and its ductility and

* Materials for Engineering.