Brass employed for the production of fine castings requires to possess other properties than those of being able to be filed and turned in the lathe. It must be thinly liquid when melted, and not in any degree pasty, so that it will readily flow into the minutest and most intricate crevices of the mould, and the texture must be fine-grained and uniform throughout. Moreover, as such castings specially require to be sound and free from pinholes, it must be capable of remaining thinly liquid until near the point at which it solidifies, so that the metal may be poured at the lowest possible temperature, thus enabling air and other gases, absorbed during the melting, to escape as much as possible before pouring. When the castings have to be subsequently gilded, it has been found that when the metal is similar in colour to gold, it requires less gold to produce the desired effect than when the brass is of a pale yellow colour. For this reason brass of reddish-yellow colour is preferred. The French have brought the casting of fine articles, as well as larger articles, to a high degree of perfection; clock-cases, statuettes, and other artistic ornamental work are manufactured by them on an extensive scale. The alloys used for these purposes are often called bronze, but they are generally brass, with the addition of a little lead and tin, which impart to the metal a bronze-like colour. The following are the proportions used for a few of the French mixtures :

:

The above alloys can be readily cast, worked with files and

turning tools, and readily gilt.

"Melt

These alloys are distinguished by a beautiful gold colour which very closely resembles that of gold alloys. They are very ductile and tenacious, can readily be stamped and rolled, and admit of a fine polish. According to an old recipe orëide is prepared in the following manner : 100 parts of copper and add, with constant stirring, 6 parts of magnesia, 3.6 parts of sal-ammoniac, 18 parts of lime, and 9 parts of crude tartar. Stir again thoroughly, and then add 17 parts of granulated zinc, and after mixing it with the copper by vigorous stirring, keep the alloy liquid for one hour. Then remove the cover of dross, and pour out the alloy."

§ 31. Talmi or Talmi Gold.—Also termed Abyssinian

gold

Talmi gold is the name given by the French, who use the foregoing alloys for cheap jewellery, which is distinguished by good workmanship, great durability, and a beautiful golden colour. The colour is retained for a considerable time, as it possesses a thin coating of gold, firmly welded to the alloy by rolling, and when the gold is of sufficient thickness the characteristic appearance may be retained for years without alteration. But many cheap imitations

are manufactured and sold under this name which consist of common brass, gilded with a thin coating of gold.

§ 32. Tournay's Alloy is also used in the manufacture of cheap jewellery, as well as for buttons and so-called bronze ornaments. It is composed of 82.5 parts of copper and 17.5 parts of zinc.

§ 33. Mannheim Gold, Similor, Prince's Metal.--The composition of this alloy varies considerably, as will be seen from the following analyses of three samples :

.

The first has a yellowish-red tint, and the second one a deeper red. Similor has been much used for buttons, and other stamped work requiring a reddish cast of colour.

§ 34. Tombac.--As stated on a previous page, tombac is a name applied to alloys which by some manufacturers are termed prince's metal, similor, and Mannheim gold. The name is used for alloys so widely different in composition and properties as to lose any significance it may have formerly possessed, and strikingly illustrates the great need. of adopting Dr. Percy's proposition, that the different alloys of copper and zinc should be designated by their percentage composition. The following table will show the proportions of different mixtures:

§ 35. Gilding Metal.--Alloys of copper and zinc containing upwards of 80 per cent of copper have a reddish-yellow or red tint, and are used as a base for gilding. The more nearly the colour approaches to that of standard gold, the more highly is it appreciated for articles which are subsequently to be gilded. When such metal is required for rolling into sheet, it will be seen by reference to the table collated for the U.S. Board that the most malleable alloy is represented by the composition, 83 copper and 17 zinc. These alloys are also known by the name of red-brass, and as the reddish cast of colour is more agreeable to the eye than that of yellow-brass, they are frequently used for cast articles not requiring special hardness and strength. It has the reputation, however, of tarnishing quicker than ordinary brass. The properties of red-brass may be modified to suit special cases by the addition of tin, lead, and iron, the action of which has been already explained.

The following varieties of brass are distinguished from the preceding alloys by a characteristic yellow colour as contrasted with red brass.

§ 36. Hamilton's Metal, Chrysorin, and Mosaic Gold.

Hamilton and Parker in 1826 claimed for the 50 per cent alloy that, after casting in the mould and cooling, it exhibits the colour of gold, and does not tarnish by exposure to air, even in the neighbourhood of the sea. They prepared it by fusing together equal parts of copper and zinc in a crucible at the lowest possible temperature, stirring constantly, and then adding a further quantity of zinc in small portions, till the right colour was obtained. This alloy is

very flexible when strongly heated, but not adapted for cold rolling or wire drawing. It melts at a comparatively low temperature, and is used as a hard solder. The higher alloys given under the above names are malleable and ductile, and, as before mentioned, well adapted for cast ware.

The method of preparation described by Hamilton and Parker would be quite unsuitable for adoption on a working scale, for independently of the great waste of zinc, the composition of the alloy would be of an uncertain character. The usual plan is to melt the copper first and then add the zinc. The following plan has been recommended, but is open to serious objection for the same reasons as mentioned above. Bring into the crucible one-half of the zinc to be used; place upon this the copper, and fuse the mixture, under a cover of borax, at as low a temperature as possible. When the contents of the crucible are liquid, heat the other half of the zinc (cut into small pieces) until almost melted, and throw it into the crucible in portions; stir constantly to effect as intimate a mixture of the metals as possible.

§ 37. Prince's Metal.—A name given to various yellow alloys varying from 60 to 75 per cent of copper and 40 to 25 per cent zinc.

§ 38. Bobierre's Metal. This is ordinary brass, consisting of 66 parts copper and 34 parts zinc. Bobierre introduced this alloy as especially suitable for ships' sheathing.

§ 39. Macht's Yellow Metal is composed of 57 parts copper and 43 parts zinc. It has a reddish-yellow colour, malleable when rolled hot, but not in the cold. It is said to be suitable for fine castings, as it possesses great strength.

BRASS CONTAINING IRON

§ 40. Many samples of brass and bronze made by the ancients have been found on analysis to contain iron, and probably they knew that the addition of iron to these alloys would increase their hardness and strength, and introduced it with that view. In more modern times the combination of iron with brass has engaged the attention of metallurgists, and several alloys, containing iron as an essential constituent, have been introduced from time to time. In 1779 James Keir proposed an alloy of 10 parts iron, with 100 parts