Marvels of Modern Science | Page 8

issuing from his lips created a sound wave which the medium of the air conveyed to the tympanum of the partner of his joys and the cause of his sorrows.
When one person speaks to another the speaker causes certain vibrations in the air and these so stimulate the hearing apparatus that a series of nerve impulses are conveyed to the sensorium where the meaning of these signals is unconsciously interpreted.
In wireless telegraphy the sender causes vibrations not in the air but in that all-pervading impalpable substance which fills all space and which we call the ether. These vibrations can reach out to a great distance and are capable of so affecting a receiving apparatus that signals are made, the movements of which can be interpreted into a distinct meaning and consequently into the messages of language.
Let us briefly consider the underlying principles at work. When we cast a stone into a pool of water we observe that it produces a series of ripples which grow fainter and fainter the farther they recede from the centre, the initial point of the disturbance, until they fade altogether in the surrounding expanse of water. The succession of these ripples is what is known as wave motion.
When the clapper strikes the lip of a bell it produces a sound and sends a tremor out upon the air. The vibrations thus made are air waves.
In the first of these cases the medium communicating the ripple or wavelet is the water. In the second case the medium which sustains the tremor and communicates the vibrations is the air.
Let us now take the case of a third medium, the substance of which puzzled the philosophers of ancient time and still continues to puzzle the scientists of the present. This is the ether, that attenuated fluid which fills all inter-stellar space and all space in masses and between molecules and atoms not otherwise occupied by gross matter. When a lamp is lit the light radiates from it in all directions in a wave motion. That which transmits the light, the medium, is ether. By this means energy is conveyed from the sun to the earth, and scientists have calculated the speed of the ether vibrations called light at 186,400 miles per second. Thus a beam of light can travel from the sun to the earth, a distance of between 92,000,000 and 95,000,000 miles (according to season), in a little over eight minutes.
The fire messages sent by the ancients from hill to hill were ether vibrations. The greater the fires, the greater were the vibrations and consequently they carried farther to the receiver, which was the eye. If a signal is to be sent a great distance by light the source of that light must be correspondingly powerful in order to disturb the ether sufficiently. The same principle holds good in wireless telegraphy. If we wish to communicate to a great distance the ether must be disturbed in proportion to the distance. The vibrations that produce light are not sufficient in intensity to affect the ether in such a way that signals can be carried to a distance. Other disturbances, however, can be made in the ether, stronger than those which create light. If we charge a wire with an electric current and place a magnetic needle near it we find it moves the needle from one position to another. This effect is called an electro-magnetic disturbance in the ether. Again when we charge an insulated body with electricity we find that it attracts any light substance indicating a material disturbance in the ether. This is described as an electro-static disturbance or effect and it is upon this that wireless telegraphy depends for its operations.
The late German physicist, Dr. Heinrich Hertz, Ph.D., was the first to detect electrical waves in the ether. He set up the waves in the ether by means of an electrical discharge from an induction coil. To do this he employed a very simple means. He procured a short length of wire with a brass knob at either end and bent around so as to form an almost complete circle leaving only a small air gap between the knobs. Each time there was a spark discharge from the induction coil, the experimenter found that a small electric spark also generated between the knobs of the wire loop, thus showing that electric waves were projected through the ether. This discovery suggested to scientists that such electric waves might be used as a means of transmitting signals to a distance through the medium of the ether without connecting wires.
When Hertz discovered that electric waves crossed space he unconsciously became the father of the modern system of radio-telegraphy, and though he did not live to put or see any practical results from his wonderful discovery, to him in