336 Electro-Magnetic Experiments. 



tirely independent of each other. Perhaps a few years later, and it 

 will be generally known that many of these disjoined facts are pro- 

 duced by the same general cause. 



Since the days of Gilbert, it has been allowed that the earth acts 

 on magnets near its surface, as one magnet on another. Every one 

 knows what is meant by the magnetism of the earth. Thus the globe 

 of the earth acts as a system of magnets whose poles are placed in a 

 certain determined position with respect to the terrestrial poles. 



But a magnet, when acted on by galvanism, may be made to re- 

 volve round its axis. May not, therefore, the revolution of the earth, 

 of that immense magnet, be effected by galvanism by a similar cause? 



Magnetic inclination and declination may be produced by galvan- 

 ism. The magnetic needle is subject to inclination and variation on 

 the surface of the earth. A magnet revolves on its axis when under 

 the influence of galvanism ; the earth revolves also on its axis. 



The light produced by galvanism is unrivalled by any other artifi- 

 cial light. No argand or any other lamps, or gas light, can be com- 

 pared to that emitted by charcoal placed between the poles of a large 

 galvanic apparatus. The light of the sun alone is superior to it. 

 Galvanic light in a vacuum will extend itself to greater distances, and 

 its appearance is strikingly similar to that of that light which is obser- 

 ved in the vicinity of the magnetic poles of the earth, of the aurora 

 borealis. 



To complete the analogy, the emission of this polar light has an 

 influence on the magnetic needle, which cannot be doubted after the 

 repeated experiments of M. Arago. 



Would it be entirely absurd to suppose that aurora borealis is 

 produced in those places where the galvanic force, which determines 

 the rotation of the earth, is communicated to the globe ? 



No lamp nor gas light acts on the Bolognese stone, nor on Canton's 

 phosphorus. These bodies imbibe light only by exposure to the 

 sun's rays. But the same effect may be produced by exposing 

 the Bolognese stone or Canton's phosphorus to the action of gal- 

 vanic or electric light. Thus galvanic light alone possesses this anal- 

 ogy with sun light; and galvanic force is alone capable of producing 

 on a smaller scale the same effects which are dependent on the action 

 of the sun's rays. 



Since Mrs. Somerville repealed Morrichmrs experiments, and 

 pointed out the method of making them with certainty of success, it 

 is scarcely possible to doubt the power of the sun's rays refracted 

 through a prism of magnetizing steel needles. Thus magnetism is 



