Wireless Telegraphy and Telephony

WIRELESS TELEGRAPHY 3 Light is known to be vibrations of an extremely rapid period—electromagnetic waves, they are called. Heat can be shown to be of the same nature. Traveling at the rate of over 180,000 miles per second, these two great gifts of the sun come streaming continually clown to us over the inconceivable distance of almost 100,000,000 miles. Both require a medium for their propagation. The ether supplies it. It is the substance with which the universe is Fig. 2.—A Leyden jar is a glass jar lined inside and out with tinfoil for about two-thirds of its height. filled. Incidentally it is also the seat of all electrical and magnetic forces. In throwing the stone into the pool of water, muscular energy of the arm is transferred to the stone, and the latter, upon striking the surface of the pond, imparts a portion of that stored energy, to the little waves which are immediately created in the water. In setting up electro- magnetic waves for wireless communication the energy im- parted to the ether is electrical energy, developed by cer- tain interesting instruments explained further on. Let us consider briefly how the waves are created in a wireless telegraph station. Almost every, one has seen and