We lately published a short description of a very interesting apparatus which may be considered in some sense as a prototype of the Gramme machine, although it has very considerable, indeed radical differences, and which, moreover, was constructed for a different purpose, the Elias machine being, in fact, an electromotor, while the Gramme machine is, it is almost unnecessary to say, an electric generator. This apparent resemblance makes it, however, necessary to describe the Elias machine, and to explain the difference between it and the Gramme. Its very early date (1842), moreover, gives it an exceptional interest. The figures on the previous page convey an exact idea of the model that was exhibited at the Paris Electrical Exhibition, and which was contributed by the Ecole Polytechnique of Delft in the Dutch Section. This model is almost identical with that illustrated and described in a pamphlet accompanying the exhibit. The perspective illustrations show the machine very clearly, and the section explains the construction still further. The apparatus consists of an exterior ring made of iron, about 14 in. in diameter and 1.5 in wide. It is divided into six equal sections by six small blocks which project from the inner face of the ring, and which act as so many magnetic poles. On each of the sections between the blocks is rolled a coil, of one thickness only, of copper wire about 0.04 in. in diameter, inclosed in an insulating casing of gutta percha, giving to the conductor thus protected a total thickness of 0.20 in.; this wire is coiled, as shown in the illustration. It forms twenty-nine turns in each section, and the direction of winding changes at each passage in front of a pole piece. The ends of the wire coinciding with the horizontal diameter of the ring are stripped of the gutta percha, and are connected to copper wires which are twisted together and around two copper rods, which are placed vertically, their lower ends entering two small cavities made in the base of the apparatus. The circuit is thus continuous with two ends at opposite points of the same diameter. The ring is about 1.1 in. thick, and is fixed, as shown, to two wooden columns, B B, by two blocks of copper, a. [Illustration: THE ELIAS ELECTROMOTOR.--MADE IN 1842.]