The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

498 ELECTRIC CURRENTS.
Fig. 1.
l c-,S * lI_
<-~ -c-.<- __.
O-s I- ( - C-
cells to obtain intensity of current sufficient to overcome the
losses occasioned by the fog. The current escapes through the
does not exactly represent the case, but it is sufficiently correct to enable the reader to form an idea as to the "leaking"
of the current from the wire through the fog to the earth.
Heat has frequently produced the same result as mentioned
above. On some lines in America, during very hot days, in the
afternoon, when everything was dry and all surface moisture
absorbed by the rays of the sun, I have known it to be impossible to work on a well-insulated line as far as two hundred
miles. The result may not have been the heat, but there is
no other way to account for it. The metallic circuit was good,
because at times when it was dry and cool, or when it rained,
and during the morning hours, there was no difficulty in workFig. 2.,u.E. —- I- -~-. — -----------.moisture. If it was not the heat, I know of no means of accounting for the strange phenomena which so often and for so
many weeks manifested itself.