Military telegraph lines using the polarized sounder as receiving instrument

It is well known that, in time of war, the army has considerable difficulty in keeping up its overland telegraph lines, and especially so if these lines are operated on the ordinary Morse system and with wet cells. In actual warfare, in the field, all impedimenta must be reduced to a minimum, and consist of as little perishable material as possible. If, for example, it is desired to operate a closed circuit line of say 300 miles in length about 150 gravity cells would be required, and if the line were to be operated on open circuit it would require about 100 dry cells per station. On the other hand induction telegraphy, so called, allows such a line to be successfully operated with from four to six dry cells per station. This fact and other features of simplicity which it possesses explains the existence of army field induction telegraphy.