states "that the tendency to shoot into fibres extends from alloys containing 57 or 58 per cent of copper down to those containing 43 to 44 per cent, where it gradually disappears. The inclination to form fibres is strongest in those alloys which contain nearly equal atomic proportions of copper and zinc, being less clearly marked as one recedes in either direction from this point, until a stringy texture, analogous to that of copper, is reached on one hand, and the peculiar pastiness of zinc on the other. In preparing crystals, this pastiness manifests itself decidedly in the alloys immediately below those which are fibrous, becoming more strongly marked as the alloys are richer in zinc. The fracture of these white alloys is for the most part vitreous or glassy."

Brass is occasionally obtained in crystals. Storer prepared the most perfect individual crystals from brasier's solder, which consists of equal parts by weight, of copper and zinc, and occurs in the state of coarse powder, produced by heating the alloy to a sufficient degree and pounding it in a mortar while hot. The alloy containing 5 to 6 per cent of zinc was found to crystallise remarkably well. It will be seen from the above remarks that the crystalline condition of copper-zinc alloys does not depend on an excess of zinc, as might be presupposed from the highly crystalline character of zinc. As before stated, zinc becomes malleable when worked at a temperature of from 100° to 150° C., but at higher temperatures it again becomes brittle. It is assumed that the brittleness is intimately connected with the crystalline condition. Kalischer examined different varieties of sheet brass having the following composition :

Nos. I and II were crystalline, No. III showed traces of

crystallisation, and No. IV did not become crystalline even

In the above specimens no crystallisation could be detected.

The tensile strength of copper-zinc alloys is widely divergent; the greatest strength, according to Mallet, is obtained in the alloy containing 32.85 per cent copper, but this is very probably a mistake, and the greatest tenacity is in alloys containing upwards of 50 per cent copper.

§ 24. The following table of the composition and properties of copper-zinc alloys is taken from Mr. Mallet's table and Karsten's observations 1:

1 Percy's Metallurgy, p. 611.

column 6 represent intensity of tint of the same colour. In column 7 the letters are abbreviations for the characters of the fractures according to Mallet's nomenclature, thus F.F.

fine-fibrous, C. conchoidal, V.C. vitreous-conchoidal, F.C. fine-crystalline, C.C. coarse-crystalline. The tensile strength was determined on prisms inch square, without having been hammered or compressed after being cast; and the weights given are those which each prism just sustained for a few seconds before disruption.

"6. Approaching tombac in colour, is not quite so good for rolling, hammering, or wire drawing as common red brass, which contains less copper in proportion to the zinc.

"8. Comes very near 'red-brass,' which it quite equals with respect to its working qualities.

"10. The reddish colour is now beginning to pass into brass-yellow; it behaves itself irreproachably under the rolls and hammer, and in wire drawing.

"13. Working qualities quite the same as those of common brass. Karsten remarks that it was this alloy which was puffed for some time in England under the name of Mosaic gold.

"14. In working qualities not different from common brass.

"16. It contains 4 per cent more zinc and 4 per cent less copper than common brass. The colour is no longer pure brass-yellow, but has a reddish tint, works excellently under the rolls and hammer, as well as in wire drawing.

"19. Much to be recommended, on account of its golden colour, and though it possesses greater tenacity than the preceding, and less hardness, is brittle. Well adapted for cast ware. Very flexible after casting while still hot. When cold it is hard to cut, and is rather fractured than cut. The ingots after being cut, annealed, and cooled, can no longer be rolled. If, after heating and cooling to the temperature of boiling water, they are rolled, they produce only very brittle, fragile sheets, much cracked at the edges, notwithstanding that frequent annealing during rolling may have been resorted to; it is quite unsuitable for rolling, hammering, or wire drawing.

"20. Very flexible while strongly heated. Rolls tolerably

well cold, though it frequently cracks at the edges. During rolling into thin sheets, it requires more frequent annealing than common brass. It cannot be soldered, as it melts at the same temperature as the solder. It is not adapted for wire drawing.

"21. Fracture reticulated.

Possesses a tolerable degree

of tenacity, but by hammering becomes so brittle that at no temperature can it be sufficiently drawn out for practical

purposes.

"22. The lustre is so imperfectly metallic, that it would hardly be recognised as a metallic alloy. Its great brittleness and frangibility, combined with its perfectly conchoidal and smooth fracture, communicate to the alloy more the appearance of a sulphur compound than that of a mixture of two metals.

"23. More brittle than the last; fracture smooth, even, small-conchoidal; lustre strongly metallic.

"25, 26, 27. Very brittle. Too hard to file or turn; lustre nearly equal to that of speculum metal.

"28, 29. Brittle. Too hard to file or turn; lustre nearly equal to that of speculum metal.

"30. Very brittle. Too hard to file or turn; lustre nearly equal to that of speculum metal.

"31. Barely malleable.

"32. Brittle; fracture granular, uneven; has a tolerable degree of tenacity, but cannot be worked under the rolls or hammer.

"33. Brittle.

"34. In external character and working qualities closely resembles No. 32.

"36. Brittle.

"38. Fracture finely granular.

"39. Has sufficient tenacity to admit of being somewhat extended under the rolls and hammer, if, after annealing, it is not allowed to become cold."