See Dr. Edward's Paper on Speculums, published in the Nautical Almanack, 1787, reprinted in Gill's Technological Repository, vol. i. p. 240, and 264. See likewise Lord Oxmantown's Paper, Trans. Royal Society, 1840, pp. 503 - 527.

32 os. of tin to one pound of copper, make the alloy called by the pewterers "tember," which is added in email quantities to tin, for some kinds of pewter, called " tin and tember," in which the copper is frequently much less than 1 per cent, See Pewter, page 284, and mixing the same, page 810.

Remarks Os The Alloys Of Copper Amd Tin Only

Theae metals seem to mix in all proportions.

The addition of tin continually increases the fusibility, although when it is added cold it is apt to make the copper pasty, or even to set it in a solid lump in the crucible.

The red colour of the copper is not greatly impaired in those proportions used by the engineer, namely, up to about 2 1/3 ounces to the pound; it becomes greyish white at 6, the limit suitable for bells, and quite white at about 8, the speculum metal, after this, the alloy becomes of a bluish cast

The tin alloy is scarcely malleable at 2 ounces, and soon becomes very bard, brittle, and sonorous; and when it has ceased to serve for producing sound, it is employed for reflecting light

The tough tenacious character of copper under the tools rapidly gives way; alloys of 1 1/2 cut easily. 2 1/2 assume about the maximum hardness without being crystalline; after this they yield to the file by crumbling in fragments rather than by ordinary abrasion in shreds, until the tin very greatly predominates, as in the pewters, when the alloys become the more flexible, soft, malleable, and ductile, the less copper they contain.

Alloys of Copper and Lead only. (Note. - The marginal numbers denote the ounces of lead added to every pound of copper.)

2

oz.

A red-coloured and ductile alloy.

4

oz.

Lew rod and ductile; neither of these is so much used as the following, as the object is to employ as much lead as possible.

6

oz.

Ordinary pot-metal, called dry pot-metal, as this quantity of lead will be taken up without separating on cooling; this is brittle when warmed.

7

oz,

This alloy is rather short, or disposed to break.

8

oz.

Inferior pot-metal, called wet pot-metal, as the lead partly oozes out in cooling, especially when the new metals are mixed; it is therefore always usual to fill the crucible in part with old metal, and to add new for the remainder This alloy is very brittle when slightly warmed. More lead can scarcely be used as it separates on cooling.

Remarks ON the Alloys of Copper and Lead only.

These metals mix in all proportions until the lead amounts to nearly half; after this they separate in cooling.

The addition of lead greatly increases the fusibility.

The red colour of the copper is soon deadened by the lead; at about 4 ounces to the pound the work has a bluish leaden hue when first turned, but changes in an hour or so to that of a dull gun-metal character.

When the lead does not exceed about 4 oz. the mixture is tolerably malleable, but with more lead it soon becomes very brittle and rotten: the alloy is greatly inferior to gun-metal, and is principally used on account of the cheapness of the mixture, and the facility with which it is turned and filed.

Alloys of Copper, Zinc, Tin, and Lead, etc.

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.

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

Copper. .

91.40 or about

14 3/4

ounces.

Zinc . . .

5.53

,,

1

,,

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 colour. (Ure.)

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

11 /2

oz. tin

1/2 zinc to 16 oz.

copper.

Pumps and works requiring great tenacity.

4

oz. tin

2 oz.

brass

16

,,

For wheels to be cut into teeth.

1 3/4

,,

2

,,

16

,,

2

,,

1 1/2

,,

16

,,

For turning work.

2 1/4

,,

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 numbers 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 by a celebrated engineer; it is made by mixing 1 1/2 lb. tin, 1 1/2 lb. zinc, and 10 lb. of copper; the alloy is first run into ingots.

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

2 1/4 oz. tin, 2 1/2 oz. zinc, to 1 lb. copper, were mixed by the late Sir F. Chantrey, and a razor was made from the alloy; it proved nearly as hard as tempervd steel, and exceedingly destructive to new files, and none others would touch it. (Wilkinson.)

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 ditto. (Philhpa's Dictionary.) 10 lb. tin, 6 lb. copper, 4 lb. brass constitute white solder. The copper end brase ere first melted together, the tin is added, end the whole stirred end poured through birch twigs into water to granulate it; it is afterwards dried and pulverised 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 parte copper, 8 of brass, and 12 of spelter or sine.

Remarks on Alloys or Copper, Zinc. Tin, and Lead. etc.

Ordinary Yellow Brass, (copper and zinc,) is rendered very sensibly harder, so as not to require to be hammered, by a small addition of tin, say 1/4 or 1/2 ox. to the lb. On the other hand, by the addition of 1/4 to 1/4 oz. of lead, it becomes more malleable and casts more sharply. Brass becomes a little whiter for the tin, and redder for the lead. The addition of nickel to copper and sine constitutes the so-called German silver. See Nickel, page 279.

Gun Metal, (copper and tin,) very commonly receives a small addition of zinc; this makes the alloy mix better, and to lean to the character of braes by increasing the malleability without materially reducing the hardness. The standard measures for the Exchequer were made of a tough alloy of this kind. The sine, which is sometimes added in the form of brass, also improves the colour of the alloy, both in the recent and bronzed states. Lead in small quantity improves the ductility of gun-metal, but at the expense of its hardness and colour; it is seldom added. Nickel has been proposed as an addition to gun-metal by Mr. Donkin, and antimony by Dr. Ure.