We must bear in mind that, as far as the ratio and idea of employment of a transformer are concerned, the problem at that time was quite another to what it is now. At present the transformer serves principally to render possible the carrying of the current to a great distance economically. The electricians of those days were not so far advanced as to be able to run arc lamps independently of one another on the same circuit, and this they held to be quite impossible, whether the lamps were connected in parallel or series. That apparatus was thought to be good which allowed separately insulated currents to be led from one source of current, each separate circuit going to feed a single lamp. The chief reason for this view lay in the fact that the extinguishing of all the lamps in one circuit could easily take place through the fault of one of them. At that time, when an arc lamp was cut out of circuit, it was replaced by a fixed resistance, instead of which it was thought that induction coils would have suited well. It may be casually mentioned that owing to this fact too sanguine hopes of the solution of the problem of independent working of lamps were aroused, through a want of sufficient knowledge of the laws of induction. There have also been apparatus other than induction coils used for the purpose of making the points of consumption independent of one another. We can only now recall the patent of Jablochkoff, No. 1638, which is based on the principle of connecting condensers into branches of a quickly alternating main current, from which arc lamps, &c., were fed; also a like arrangement by Avernarius (Figs. 16 and 17), with the use of secondary batteries, which were to be employed for either parallel or series connection.[2] [Illustration: FIG. 16.] [Illustration: FIG. 17.] There were no transformers in those days which, in the present sense of the word “transformer,” convert high electromotive force to low to suit the consumers. On the contrary the apparatus, which was then used in electric lighting plant, was such as converted low into high electromotive force, or such that the ratio was 1:1, or nearly so, according as it was determined by the connection in series of the primary coils, and the difference of potential at the consumption devices; for example, the induction coils of B. Ruhmkorff, Jablochkoff, and Gordon.