In April, 1895, a communication was made to the Russian Physical
Society by Prof. A. Popoff, of the Torpedo School, Cronstadt, Russia,
and appears in the _Journal_ of that Society for January, 1896. In this
communication the use of an elevated wire and of a tapper-back worked
through a relay by the coherer current are clearly described, and
signalling was effected for a distance of 5 kilometres (3½ miles).
An extract from this communication is given in _The Electrician_ for
December, 1897, Vol. XL., page 235, and from it we reproduce Fig. 42,
illustrating the tapping back arrangement.