are placed one on either side of the electrodes; the charge is put in between them, and the charcoal is then filled in between the sheet-iron and the sides of the furnace, after which the sheet-iron is withdrawn, the top of the charge covered, and the ends of the furnace filled with charcoal to the depth of a few inches above the charge and the electrodes. The iron cover is then luted on with fire-clay. A current of 2000 to 3000 amperes is applied at first, and, as the charge becomes fused, the resistance diminishes. The electrodes are then drawn farther apart, the speed of the engine increased, and a current of 5000 amperes flows through the charge, until the whole of the ore and metal are fused. One operation requires about one hour and three-quarters. It is assumed that the aluminium and copper unite when both are in the gaseous state, and the Company claim that by this means a completeness of union between the constituents of the alloy, and a homogeneity and strength are obtained superior to alloys formed in any other way."

The rich alloys prepared in the electrical furnace just described are used for making aluminium-bronze, brass, and iron, by melting them with copper, tin, zinc, etc., in a crucible in an ordinary furnace, instead of using pure metallic aluminium, and it is found by this means that more perfect and uniform alloys are obtained.

ALUMINIUM-BRASS

§ 80. This alloy is prepared by adding spelter to aluminiumbronze, or by melting together various proportions of ordinary brass and aluminium-bronze. The greater the proportion of the bronze present in admixture, the harder and stronger the brass becomes. Alloys containing copper, zinc, and aluminium between the following limits—

Copper
Zinc
Aluminium.

67 to 71

31 to 25

1 to 3

and combined in different proportions, have a tensile

strength varying from 13 to 30 tons per square inch. Alloys with 56 to 57 per cent copper and 40 to 42 per cent zinc approach nearer 31 tons tensile strength. Mr. Robey states that aluminium-brass is composed of of 10 per cent aluminium-bronze, copper, and spelter.

Aluminium-brass is close-grained, homogeneous, and tough, with a useful tensile strength, and great elastic resistance. With regard to transverse stress, a bar of Cowles's No. 2 brass, 1 inch square and 12 inches between supports, showed a breaking load of 72 cwts.; the deflection with 44 cwts. load was 04 of an inch, and the permanent set 01. Aluminium-brass forges hot, and, owing to its special casting qualities, low specific gravity, strength, toughness, and rigidity, is very suitable for ships' propellers, rudder frames, pumps, valves, pinions, etc., as well as for hydraulic work. With regard to casting, practically the same rules apply, as. those given for aluminium-bronze. Its working qualities, when the amount of aluminium is high, are similar to those of the bronze. The working qualities are also governed largely by the quantity of zinc contained in the brass-the higher the percentage of zinc, the harder the metal, and the shorter the chip which flies from the tool.

Hercules Metal.--This is a cheaper form of aluminiumbrass made by the Cowles Company. It casts well, and whilst very hard and strong, works well under the tool. It is malleable when hot, and suitable for all castings where a strong metal is required. Its tensile strength varies from 30 to 40 tons per square inch; with an elongation of 10 to 30 per cent, according to the proportions of the constituents. It contains a proportion of iron as high as 7 per cent, together with a larger proportion of spelter than in the ordinary brass.

§ 81. The following tests were made by order of the navy department of the United States, and the table shows the favourable results of aluminium bronze and brass as compared with gun-metal.1

1 Paper by Mr. Dagger, Brit. Assoc. 1889.

Approximate Composition.

Cu.

Al.

Si.

Zn.

Sn.

inches.

inch.

Aluminium alloys containing varying proportions of nickel are made, and are said to be very ductile and to possess a tenacity of from 33 to 44 tons per square inch. Tests made by Kircaldy on similar alloys, manufactured by the "Crown Metal Company," gave results ranging from 39 to 42 tons per square inch. According to Mr. Webster, two alloys are employed by the Company for preparing the bronze, designated as aluminium alloy A and nickel alloy B. The A alloy consists of 15 parts aluminium and 85 parts tin. The B alloy consists of 17 parts nickel, 17 parts copper, and 66 parts tin. The metals are melted in the usual way with the use of a flux, under a cover of common salt and potassium chloride. The two alloys are then melted together with copper. It has been found that the bronze is the harder and better the more it contains of the two alloys, and vice versa. The following is recommended as the best proportion : copper, 88 parts, and 8 parts of each of A and B. The copper is first melted and the alloys added; the mixture is then stirred with a wooden or clay rod (an iron rod must not on any account be used) until the mass is homogeneous, as shown by a test-ingot. A second quality alloy, which is cheaper than the preceding, is composed of 92 parts copper, and 4 parts each of the alloys A and B.

One great drawback to the use of aluminium-bronzes for manufactured articles is the difficulty experienced in soldering and brazing them. The Cowles Electric Smelting Company has issued the following directions :

:

§ 82. Brazing.-Aluminium-bronze will braze as well as any other metal by using brass solder (copper 50 per cent, zinc 50 per cent), and borax.

§ 83. Soldering.—To solder aluminium-bronze with soft solder cleanse well from dirt and grease the parts to be joined. Then place the parts to be soldered in a strong solution of sulphate of copper, and place in the bath a rod of soft iron, touching the parts to be joined. After a while a copper-like surface will be seen on the metal. Remove

from bath, rinse quite clean, and brighten the surfaces. These surfaces can then be tinned by using a fluid, consisting of zinc dissolved in hydrochloric acid, in the ordinary way, with soft solder.

Mierzinski says that Hulot uses an alloy of the usual half-and-half lead and tin solder, with 12, 25, and 50 per cent of zinc amalgam.

CHINESE AND JAPANESE BRONZES

§ 84. The Chinese and Japanese have attained great perfection in making bronzes for art metal-work, of which the following may be taken as typical. The first is called shakudo, and contains

The above have been used for very large works of art, such as colossal statues. Professor Roberts-Austen states that the quantity of gold is very variable, some specimens which he analysed containing only 1.5 per cent gold. The other alloy is termed shibu-ichi, of which there are many varieties. The precious metals are employed to produce definite results.