The commutator is 20 inches long, and has sixty-four parts.  The current is collected by eight brushes mounted on a separate ring, placed concentric to the commutator; and the current is led away from these brushes by a large number of thin bands of sheet copper strapped together into convenient groups.  The field magnets are of the horizontal double type.

As this machine is virtually a series wound machine, the magnet coils each consist of a few turns only of forged copper bars, 11/2 in. wide by 1 in. thick, forged to fit the magnet cores.

There is no insulation other than mica wedges to keep the bars from touching the core.

The dynamo furnishes a current of about 5,000 amperes, with an E.M.F. of 50 to 60 volts, and three years ago was claimed to be the largest machine, at least as regards quantity of current, in the world.

The current from the dynamos is led by copper bars to an enormous “cut out,” calculated to fuse at 8,000 amperes.  This is probably one of the largest ever designed, and consists of a framework carrying twelve lead plates, each 31/2 in. x 1/16th in. thick.  A current indicator is inserted in the circuit consisting of a solenoid of nine turns.  The range of this indicator is such that the center circle of 360 deg.=8,000 amperes.

The electrodes consisted of a bundle of nine carbons, each 21/2 in. in diameter, attached by casting into a head of cast iron.  Each carbon weighs 20 lb, and, when new, is about 48 inches long.

The head of the electrode is screwed to the copper rods or “leads,” which can be readily connected with the flexible cable supplying the current.

The electric furnaces are rectangular troughs built of fire brick, their internal dimensions being 60 in. x 20 in. x 36 in. deep.  Into each end is built a cast iron tube, through which the carbon electrodes enter the furnace.

The electrodes are so arranged that it is possible by means of screwing to advance or withdraw them from the furnace.

The whole current generated by the great dynamo of the Cowles Company was passed through the furnace.

In the experiments raw materials only were used, for it was evident that it was only by the direct production of phosphorus from the native minerals which contain it, such as the phosphates of lime, magnesia, or alumina that there was any hope of superseding, in point of economy, the existing process of manufacture.

In the furnaces as used at Milton much difficulty was experienced in distributing the heat over a sufficiently wide area.  So locally intense indeed was the heat within a certain zone, that all the oxygen contained in the mixture was expelled and alloys of iron, aluminum, and calcium combined with more or less silicon, and phosphorus were produced.  Some of these were of an extremely interesting nature.

We now turn to a short account of the works and plant which have been erected near Wolverhampton to prove the commercial success of the new system of manufacturing phosphorus.