Wireless Telegraphy and Telephony

WIRELESS TELEGRAPHY 9 in turn, set up a state of strain in the surrounding ether, and cause the waves to travel out from the system. Fig. 8.—If a cross section of the aerial and atmosphere could be made in the same manner that an apple is sliced with a knife and the waves held stationary, they would appear as above. These waves follow the contour of the earth, and so may- cross mountains and valleys, and travel anywhere. They radiate from the aerial like the ripples from a pebble in a pool of water, in gradually enlarging circles. If a cross section of the aerial and atmosphere could be made in the same manner that an apple can be sliced with a knife, and the waves held stationary long enough to see them, they would appear as in Fig. 8. The curved lines represent the lines of strain induced by the oscillations. Each group of lines represents a wave. It will be noticed as they radi- ate farther from the aerial that they become larger and spread out. Fig. 9.—Under the same conditions, but when viewed from above, the appearance would be that of a series of concentric circles.