ELECTRICITY. 193 



CHAPTER IX. 



ELECTRICITY. 



Discovery of Electrical Force Diffused through all Matter 

 What is Electricity ? Theories Frictional Electricity 

 Conducting Power of Bodies Hypothesis of two Fluids 

 Electrical Images Galvanic Electricity Effects on Ani- 

 mals Chemistry of Galvanic Battery Electricity of a 

 Drop of Water Electro-chemical Action Electrical Cur- 

 rents Thermo-Electricity Animal Electricity Gymnotus 

 Torpedo Atmospheric Electricity Lightning Conductors 

 Earth's Magnetism due to Electrical Currents Influence on 

 Vitality Animal and Vegetable Development Terrestrial 

 Currents Electricity of Mineral Veins Electrotype In- 

 fluence of Heat, Light, and Actinism on Electrical Phenomena. 



IF a piece of amber, electrum, is briskly rubbed, it 

 acquires the property of attracting light bodies. This 

 curious power excited the attention of Thales of Miletus ; 

 and from the investigations of this Grecian philosopher 

 we must date our knowledge of one of the most impor- 

 tant of the natural forces Electricity. 



If an inquiring mind had not been led to ask why 

 does this curious natural production attract a feather, the 

 present age, in all probability, would not have been in 

 possession of the means by which it is enabled to trans- 

 mit intelligence with a rapidity which equals the poet's 

 dream of the " swift- winged messengers of thought." 

 To this age of application a striking lesson does this 

 amber teach. Modern utility would have regarded 

 Thales as a madman. Holding a piece of yellow resin 

 in his hand, rubbing it, and then picking up bits of down, 

 or catching floating feathers, the old Greek would have 



