The Evolution of Electric and Magnetic Physics. 167 



every-day experience with telephone-users who hear what is being said 

 on wires contiguous to their own. Without apparent connection the 

 message jumps from wire to wire through vacant space. But such 

 telegraphing without wires has been discounted very much in the 

 sending of messages to considerable distances across the sea without a 

 cable. This was done not long ago from the Isle of Wight to the 

 mainland of England. It is seriously proposed to adopt the same plan 

 by ocean ships so that they can telegraph to each other on sight. A 

 few years ago an enthusiastic individual suggested the possibility of 

 sending oceanic electric currents from America to Europe by having 

 wires and currents of sufficient power strung along the coasts of the 

 Eastern and Western Hemispheres and grounded in the water at each 

 termination. 



In theoretical considerations this department of science has until 

 lately made little or no progress. The two-fluid theory of Symmer 

 and the one-fluid theory of Franklin, while held by various students 

 and workers with less or more tenacity, were practically driven from 

 the field by the doctrine of the conservation of energy. Educated 

 electricians now generally believe that all they have to deal with is 

 modes of motion in matter and in the universal ether. Clerk Maxwell's 

 theory of light shows how it can be understood as related to and of a 

 kind with electricity. The acceptance of this theory forces us to con- 

 clude that every chemical transformation sends out from itself two 

 sets of strains on the ether answering to two forms of force, one of 

 which we call heat or light, and the other electricity. One is longi- 

 tudinal and the other transverse. It is not possible to give by mere 

 verbal description to this audience other than a rough analogous adum- 

 bration of the theory. Imagine a set of elastic cogwheels reaching the 

 length of the church and caused to revolve. The matter of the wheels 

 goes up and down by their rotation. If at the same time they are 

 crowded outward and give to the pressure, a to-and-fro movement of 

 the substance of the wheels is added to the up-and-down movement of 

 rotation. Some such two sets of movements are set up in matter and 

 the ether answering to electricity and light. The truth of Maxwell's 

 theory has almost met complete experimental proof within the last two 

 or three years. Dr. Henry Hertz, in a communication to the Sixty- 

 second Congress of German Naturalists and Physicians, which assem- 

 bled at Heidelberg last summer, communicated the results of his 

 experiments in this field of research. He showed that it was now pos- 

 sible to duplicate with electricity nearly every experiment depended 

 upon to demonstrate the truth of the undulatory theory of light. 

 Electric waves are shown under proper conditions to possess all the 

 properties of light waves. They have been reflected, refracted, made 



