290 HENKY A. KOWLAND 



So, with electricity, we must have a very violent electrical vibration 

 before waves carrying much energy are given out. 



Such a vibration we find when a spark passes from one conductor 

 to another. The electrical system may be small in size, but the im- 

 mensely rapid vibrations of millions of times per second, like the quick 

 vibration of a bee's wing, sends out a volume of waves that a slowly 

 moving current is not capable of producing. The velocity of these 

 waves is now known to be very nearly 300,000 kilometers per second. 

 This is exactly the velocity of waves of light, or other radiation in 

 general, and there is no doubt at present in the minds of physicists 

 that these waves of radiation are electromagnetic waves. 



By this great discovery, which almost equals in importance that of 

 gravitation, Maxwell has connected the theories of electricity and of 

 light, and no theory of one can be complete without the other. Indeed 

 they must both rest upon the properties of the same medium which 

 fills all space the ether. 



Not only must this ether account for all ordinary electrical and mag- 

 netic actions, and for light and other radiation, but it must also account 

 for the earth's magnetism and for gravitation. 



To account for the earth's magnetism, we must suppose the ether 

 to have such properties that the rotation of ordinary matter in it pro- 

 duces magnetism. To account for gravitation it must have such prop- 

 erties that two masses of matter in it tend to move toward each other 

 with the known law of force, and without any loss of time in the action 

 of the force. We know that moving electrical or magnetic bodies re- 

 quire a time represented by the velocity of light before they can attract 

 each other in the line joining them. But, for gravitation, no time is 

 allowable for the propagation of the attraction. 



But the problem is not so hopeless as it at fiist appears. Have we 

 not in two hundred and fifty years ascended from the idea of a viscous 

 fluid surrounding the electrified body and protruding arms outward to 

 draw in the light surrounding bodies to the grand idea of a universal 

 medium which shall account for electricity, magnetism, light, and 

 gravitation ? 



The theory of electricity and magnetism reduces itself, then, to the 

 theory of the ether and its connection with ordinary matter, which we 

 imagine to be always immersed in it. The ether is the medium by 

 which alone one portion of matter can act upon another portion at a 

 distance through apparently vacant space. 



Let us then attempt to see in greater detail what the ether must 

 exDlain in order that we may, if possible, imagine its nature. 



