“He had many difficulties to overcome before he succeeded in producing them in sufficiently rapid succession, but this was at last accomplished and Maxwell’s theory triumphantly vindicated.
“The electric vibrations comported themselves like light. It is true that a stone wall was as transparent for them as a sheet of glass is for ordinary light, but they were reflected by a metal plate and could be brought to a focus, etc., etc. Now this invisible light, as we may call it, is what Marconi and others have employed in their so-called wireless telegraphy, but, without Maxwell or Hertz, it would have remained undiscovered to this day.”
Historical.
Wireless telegraphy, or the transmission of signals through space by means of electric waves, is of a comparatively recent origin, although the idea of the existence of electric waves dates back some forty years ago.
In 1868 Clerk Maxwell, then Professor of Physics in Cambridge University, first published a theory showing that an intimate relation between electricity and light existed. This theory, which has received most conclusive substantiation since then by eminent physicists, is known as the electro-magnetic theory. It tells us that electric waves and light waves are similar; that they represent a transfer of energy by means of the all-pervading universal ether; that they differ radically in their effects on the physical senses in wave length and period of vibration, and that both possess the same velocity, 186,000 miles per second.
Many of the exponents of the electro-magnetic theory discussed the properties of electric waves long before they were experimentally demonstrated.
Our experimental knowledge of the existence of electric waves dates from about 1880.
Hertz, a German physicist, while working under the illustrious Helmholtz, discovered that small sparks could be made to pass between the two conductors when held near a circuit in which electric oscillations were set up. He soon discovered that this was due to the action of electric waves, and, realizing how fundamental in importance this was to the thorough knowledge of the electro-magnetic theory, he commenced a series of experimental researches which were of such a brilliant and productive nature as to mark them as amongst the most important investigations in the whole domain of science.
A number of experimenters then followed, amongst them Signor Marconi, who has since become closely identified with its practical application.