IOWA ACADEMY OP SCIENCE 
13 
combined phenomena of electric and magnetic displacements constitute what 
are now denoted as electro-magnetic waves. 
Maxwell’s mathematical discussion led to the conclusion that these electro- 
magnetic waves must have the same velocity in free space as that of light 
waves. In fact, it was even inferred that light waves were simply electro- 
magnetic waves of a given frequency. Abundant experimental eviaence has 
since been adduced to corroborate this inference, so that today we might 
properly include the subject of light in the domain of electricity and mag- 
netism. 
In 1888 Heinrich Rudolph Hertz succeeded in producing and detecting electro- 
magnetic waves by means of an open Leyden jar oscillating circuit. It is un- 
fortunate that Maxwell did not live to realize this great achievement, since 
he feared so keenly that it would never be accomplished and that his mathe- 
matical discussion would thus forever rest upon an undemonstrated hypothesis. 
Hertz not only produced electro-magnetic waves in conductors but also in 
free space. By means of a simple ingenious detector he was enabled to measure 
their length as they were transmitted from his oscillator to a reflecting con- 
ductor and back again in the form of stationary waves. He found that these 
waves, which were centimeters and meters in length, obeyed all the ordinary 
laws of light waves whose lengths are expressed in the sixth decimal of centi- 
meters. By means of simple contrivances he reproduced the phenomena of re- 
flection, refraction and polarization of such waves. 
The discovery of the transmission of electro-magnetic waves through free 
space is thus the special achievement of Hertz. Maxwell in his mathematical 
dissertation pointed out the probability of these waves, but it was Hertz who 
brought them into the realm of practical realization and application. Hertz’s 
experimental work is preeminent in its thoroughness and detailed exactness. 
It was unfortunate, indeed, to mankind that so subtile a mind should have been 
so, soon lost to civilization through his early death. Sir Oliver Lodge wrote 
of Hertz as follows: “The front rank of scientiflc workers is weaker by his 
death. Yet did he not go till he had effected an achievement which will hand 
his name down to posterity as the founder of an epoch in experimental physics.” 
In Hertz’s experiments were all the suggestions necessary to blaze the way 
toward the attainment of modern wireless telegraphy. Soon after the publica- 
tion of his Work a multitude of scientists in various parts of the world, inspired 
by Hertz’s achievements, took up the experimental investigation of these new 
phenomena. Hertz’s detector of these waves was rather crude but improved 
devices were soon forthcoming. Among these were the coheror devised by 
Edward Branley and extraordinarily sensitive to electric waves. Thus the 
last link was supplied for the practical accomplishment of one of the greatest 
and most useful inventions of civilization. 
In 1894 a young Italian, klarconi, then a student in the University of Bologna, 
witnessed a reproduction of Hertzian experiments by one of the professors in 
the physics lecture room of that institution. He was greatly impressed with 
the phenomena and was led to conceive the idea of signalling through space by 
means' of these Hertzian waves. After a careful study of the attainments 
of those who preceded him, he managed to construct an apparatus by means of 
which he succeeded in sending communications a distance of 300 feet between 
the British Post Oflice and the Thames Embankment. After many experiments 
