THE IDENTITY OF LIGHT AND ELECTRICITY. 179 



added to the country's creative wealth. But, when this lazzarone 

 is imported into the United States and set to grading an Ameri- 

 can railway, he is found to possess characteristics which may not 

 have interfered with his usefulness on the Mont Cenis Tunnel, 

 but which here become exceedingly unpractical, not to say un- 

 comfortable : and which may, as we have shown, even prove as 

 large a problem in our criminal, as his advent was, no doubt, a 

 happy thought in our industrial, economy. 







THE IDENTITY OF LIGHT AND ELECTRICITY.* 



By HENRI HEETZ. 



OUR first thought, when we speak of the relations of light and 

 electricity, is of the electric light. That is not the subject of 

 the present paper. The physicist thinks of the extremely deli- 

 cate reciprocal actions of the two forces, such as the rotation by 

 the current of the plane of polarization, or the variation under 

 the influence of light of the resistance of a conductor. In these 

 cases, however, the action is not direct, but a medium, ponderable 

 matter, is interposed. There are other closer, more intimate re- 

 lations between the two forces. It is my purpose to discuss the 

 proposition that light is in its very essence an electrical phenom- 

 enon whether it be the light of the sun, of a candle, or of a glow- 

 worm. Suppress electricity in the universe, light would disap- 

 pear ; suppress the luminiferous ether, electric and magnetic 

 forces would cease to act through space. This theory is not of 

 to-day or of yesterday, but has a long and instructive history. 

 My own experiments only mark one of the steps in its develop- 

 ment; and it is my purpose to retrace its whole evolution, not 

 one of its phases only. It is not easy in a matter of this kind to 

 be clear without omitting something essential. The phenomena 

 to be considered take place in space, in the ether itself, and are 

 not perceptible to the touch or the hearing or the sight. Reflec- 

 tion and reasoning may permit us to grasp them, but it is hard to 

 make an exact description of them. We shall endeavor, there- 

 fore, to connect them with ideas that are already known to us. 

 "We refer, therefore, first to what we already know concerning 

 light and electricity. 



We know of a certainty that light is an undulatory move- 

 ment, and that the undulations are transversal ; we have deter- 

 mined their length and their velocity ; and all that follows from 



* A communication to the Sixty-second Congress of German Naturalists and Physicians, 

 at Heidelberg. 



