8 ELEMENTS OF STATIC ELECTRICITY. 



the same electric intensity on different bodies. Sealing- 

 wax and ebonite, for instance, are quickly electrified, 

 whil-e brass is electrified slowly. The reason is analo- 

 gous to that in the illustrations just given : the brass 

 being a good electric conductor, the electricity is in- 

 stantly distributed equally over every part of its sur- 

 face, and hence the quantity at any point being small, 

 the intensity is low. But the sealing-wax and ebonite 

 being good non-conductors, the same quantity of elec- 

 tricity is concentrated on those parts of the surface 

 brought into immediate contact with the rubber, instead 

 of being equally distributed over the entire surface ; 

 and hence the intensity at those points is proportion- 

 ately increased. 



It will be shown hereafter that in static electricity 

 the electrification is on the surface. Hence, in this 

 case, electric intensity means quantity in proportion to 

 surface, whether it be the entire surface, as on a con- 

 ductor, or only those parts to which the electrification 

 is confined, as on a non-conductor. 



It must also be understood, as will be shown more 

 fully hereafter, that the term intensity is as applicable 

 to a diminution of electric energy at a given point as 

 to an increase ; in the same sense as we speak of intense 

 cold, as well as of intense heat. 



STATIC ELECTRICITY DEFINED. The terms used to 

 distinguish different classes of electric phenomena, as 

 frictional, static, galvanic, chemical, magneto, tliermo, 

 take their origin from the different methods by which 

 electricity is generated, and the various conditions under 

 which its phenomena have been observed, and should 

 not be understood as referring to any difference in 

 the nature of the electricity produced. 



