Wireless Telegraphy and Telephony

14 WIRELESS TELEGRAPHY A station which can only send 100 miles over land can send messages three or four hundred miles over the ocean. Forests exert a very decided effect upon the electric waves. Each individual tree acts as an antenna, reaching up into the air and absorbing part of the energy. The dif- ference in the range of a station during the summer months and that of the same station in winter is considerable. In Fig. 12.—The Army wireless station at Fort Gibbons, Alaska, show- ing steel lattice work mast and aerial system. summer the trees are full of sap and, being much better conductors of electricity when in this condition, act in the capacity of innumerable aerials rising in the air, and able to absorb appreciable amounts of energy. During these same months the air becomes highly ionized, in which state the air molecules carry an electric charge, and are particu- larly opaque to the waves. This condition also usually exists in the presence of sunlight, the result being that the most favorable time for the wireless transmission of mes- sages are the hours around midnight.