he problem in the beginning.

The fact should also be recalled that Dr. Herz had, from his first
experiments, recognized the efficiency of those microphonic contacts
that are obtained by the superposition of carbon disks or other
semi-conducting substances. He has employed these under different
arrangements and with very diverse groupings, but, as a general thing,
it has been the horizontal arrangement which has given him the best
effects.

Let us suppose, then, that four systems of contacts of this nature are
arranged at the four corners of an ebonite plate, C C (Figs. 1 and 2),
at A, A