This group refers principally to gun-metal alloys, to which more or less zinc is added by many engineers. The quantity of tin in every pound of the alloy, which is expressed by the marginal numbers, principally determines the hardness.

M. Keller's statues at Versailles are found, as the mean of four analyses, to consist of:

Copper ...................

91.40 or about 14 3/8

ounces.

Zinc.....

5.53

,,

1

ounce.

Tin.....

1.70

,,

0 3/8

,,

Lead.............................

1.37

,,

0 1/4

,,

In 100 parts or the 16 ounces.

1 1/2 to 2 1/4 oz. tin to 1 lb. copper used for bronze medals, or 8 to 15 per cent, tin, with the addition of 2 parts in each 100 of zinc, to improve the color.

The modern so-called bronze medals of our Mint are of pure copper, and are afterwards bronzed superficially.

1 1/2 oz. tin, 1/2 zmc to 16 oz. copper. Pumps and works requiring great tenacity.

1 1/2 oz. tin, 2 oz. brass, 16 oz. copper

For wheels to be cut into teeth.

1 3/4

,,

2

,,

16

,,

2

,,

1 1/2

,,

16

,,

For turning work.

2 1/2 " 1 1/2 16 " For nuts of coarse threads and bearings.

The engineer who uses these five alloys recommends melting the copper alone; the small quantity of brass is then melted in another crucible, and the tin in a ladle, - the two latter are added to the copper when it has been removed from the furnace. The whole are stirred together and poured into the moulds without being run into ingots. The real quantity of tin to every pound of copper is about one-eighth oz. less than the number stated, owing to the addition of the brass, which increases the proportion of copper.

1 7/8 oz. tin, 1 7/8 oz. zinc, to 1 lb. copper. This alloy, which is a tough, yellow, brassy, gun-metal, is used for general purposes. It is made by mixing 1 1/2 lb. tin, 1 1/2 lb. zinc, and 10 lbs. of copper. The alloy is first run into ingots.

2 1/2 oz. tin, 1/2 oz. zinc, to 1 lb. copper. Used for bearings to sustain great weights.

2 1/2 oz. tin, 2 1/2 oz. zinc, to 1 lb. copper, were mixed by Chantrey, and a razor was made from the alloy. It proved nearly as hard as tempered steel, and exceedingly destructive to new files, and none others would touch it.

1 oz. tin, 2 oz. zinc, 16 oz. brass. Best hard white metal for buttons.

1/2 oz. tin, 1 1/2 oz. zinc, 16 oz. brass. Common white metal for buttons.

1.0 lbs. tin, 6 lbs. copper, 4 lbs. brass, constitute white solder. The copper and brass are first melted together, the tin is added, and the whole stirred and poured through birch twigs into water to granulate it; it is afterwards dried and pulverized cold in an iron pestle and mortar. This white solder was introduced as a substitute for silver solder in making gilt buttons. Another button solder consists of 10 parts copper, 8 of brass, and 12 of spelter or zinc.