The magneto-electric machine, which I am about to describe, approximates in its general arrangements to Ladd's hand machine. In it Mr Ladd makes use of a compound Siemens' armature, consisting of two separate armatures placed in length, and revolving round the same axis, with their coils at right angles to each other. The armature revolves between the poles of an electro-magnet, of the description introduced by Mr Wilde. The electro-magnet, in the present instance, is made of a rectangular piece of boiler-plate, three-quarters of an inch in thickness, bent so as to form three sides at right angles to each other, as shown (in section) in fig. 1. The upright sides (P P' P) are nearly 9 inches high and 11 inches in length, and the top of the same length is 6 inches broad. Pieces of cast-iron (N and S) are put in the open end to form the poles of the magnet.