310 . ELECTRICITY. [SECT, xxvnr. 



SECTION XXVIII. 



Of ordinary Electricity, generally called Electricity of Tension Methods of 

 exciting Bodies Transference Electrics and Non-electrics Law of its 

 Intensity Distribution Tension Electric Heat and Light Atmospheric 

 Electricity Its Cause Electric Clouds Back Stroke Violent Effects of 

 Lightning Its Velocity Phosphorescence Phosphorescent Action of Solar 

 Spectrum Aurora. 



ELECTRICITY is one of those imponderable agents pervading 

 the earth and all substances, without affecting their volume 

 or temperature, or even giving any visible sign of its exist- 

 ence when in a latent state ; but, when elicited, developing 

 forces capable of producing the most sudden, violent, and 

 destructive effects in some cases, while in others their action, 

 though less energetic, is of indefinite and uninterrupted 

 continuance. These modifications of the electric force, in- 

 cidentally depending upon the manner in which it is excited, 

 present phenomena of great diversity, but yet so connected 

 as to justify the conclusion that they originate in a common 

 principle. 



Electricity may be called into activity by mechanical 

 power, by chemical action, by heat, and by magnetic 

 influence. We are totally ignorant why it is roused from 

 its neutral state by such means, or of the manner of its 

 existence in bodies, whether it be a material agent, vibra- 

 tions of ether, or merely a property of matter. Various 

 circumstances render it more than probable that, like light 

 and heat, it is a modification or vibration of that subtile 

 ethereal medium which, in a highly elastic state, pervades 

 all space, and which is capable of moving, with various 

 degrees of facility, through the pores even of the densest 

 substances. As experience shows that bodies in one electric 

 state attract, and in another repel each other, the hypothesis 

 of two fluids has been adopted by many philosophers ; but, 

 probably, the mutual attraction and repulsion of bodies arise 



