USEFUL ARTS. 



CHAPTER XV. 



Electricity, Magnetism, and Galvanism mutually convertible. The Force co 

 extensive with Nature. Uses of Thunder-storms. Languor .from Want ol 

 Electricity. Fractional and Voltaic Electricity. Origin of the Name. 

 Structure of the Voltaic Pile A simple Example of the Pile. Nerves of a 

 Frog's Leg. The Electric Shock, and how to produce it. The Electric Jar 

 and Battery. Animal Electricity. The Torpedo and Electric Eel. Struc- 

 ture of the Electric Apparatus. The Electric Spark obtained from both 

 Fishes. Channels of Electricity in the Body. The Will and the Muscles. 

 Electricity the conducting Agent. The Human Body permeated by Nerves. 

 Telegraph Wires and the Nervous System. Lightning and the Electric 

 Spark. The Electric Light and its Power. The Fire-fly, the Glow-worm, 

 and the luminous Inhabitants of the Sea. Magnetism and Diamagnetisrn. 

 The Electric Telegraph and the Compass. The Principle identical in both 

 Instruments. 



ELECTRICITY AND MAGNETISM. 



IT has long been known that Electricity, Galvanism, and 

 Magnetism are but different manifestations of the same 

 force, and that one can be converted into the other at will. 

 It is also known that this wonderful and most important 

 principle lies latent in everything, and only needs the proper 

 machinery to evoke it. 



The few following illustrations are intended to show its 

 prevalence in Nature, and that human art does not create, but 

 only makes manifest a power that exists, but lies latent until 

 called forth. 



Without going into details, which would occupy the whole of 

 such a volume as this, I may mention that Electricity saturates 

 all the material creation, and that even man himself is not 

 only a reservoir of electricity, but that he feels positively ill if 

 the normal amount be not supplied. 



Take, for example, the hours that precede a thunder-storm. 

 We feel languid and depressed. We cannot bring our thoughts 



