CHAPTER XV. 



ELECTRICITY. 



■What is Eiec 730. Electricity is one of those subtle 

 tricity? agents without weight, or form, that appear to 

 be difFused through all nature, existing in all substances 

 without aflecting their volume or their temperature, or 

 giving any indication of its presence when in a latent, or 

 ordinary state. When, however, it is liberated from this 

 repose, it is capable of producing the most sudden and 

 destructive effects, or of exerting powerful influences by 

 a quiet and long-continued action. 



HoTrmayeiec- ^31. Elcctricity may be excited, or called 

 cUed? ^^ ^^' i*^^^ activity by mechanical action, by chemical 

 action, by heat, and by magnetic influence. 

 "We do not know any reason why the means above enumerated should de- 

 velop electricity from its latent condition, neither do we know whether elec- 

 tricity is a material substance, a property of matter, or the vibration of an 

 ether. The general opinion at the present day is that electricity, Uke light 

 and heat, is the result of vibrations of an ether pervading all space. 



How is dec- 732. The most ordinary and the easiest way 

 easuy ciciTedl of cxcitiug clcctricity is by mechanical action 



— by friction. 

 How does eiec- If WO rub a glass rod, or a piece of sealing- 

 by"*^ friction wax, or resin, or amber, with a dry woolen, or 

 manifest Itself? g||^ substancc, thcsc substanccs will imme- 

 diately acquire the property of attracting light bodies, 

 such as bits of paper, silk, gold-leaf, balls of pith, etc. 



This attractive force is so great, that even at the dis- 

 tance of more than a foot, light substances are drawn to- 

 ward the attracting body. The cause of this attraction 

 is called electricity. 



Thales, one of the seven wise men of Greece, noticed and recorded tho 

 fact more than two thousand years ago, that amber when rubbed would at- 



16* 



