ELECTRICITY. 



3. Of the two species of Electricity. 



(29.) We have hitherto viewed elec- 

 trical phenomena as arising from the 

 operation of a single agent, which could 

 be called into action, and transferred 

 from one body to another. We have 

 seen that bodies, which have received 

 their electricity from excited glass, repel 

 one another, and are likewise repelled 

 by the excited glass. The same thing 

 happens with respect to those bodies 

 \vhich have received their electricity 

 from excited sealing-wax. But upon 

 examining the action of any of the bo- 

 dies belonging to the one set, upon any 

 of those belonging to the other, we find, 

 that instead of repelling, they attract 

 each other. Thus, the ball which has 

 received its electricity from the glass, 

 attracts that which has been electrified 

 by the sealing-wax, and is attracted by 

 it ; but, what is still more remarkable, 

 the moment these balls have come into 

 contact, provided they have both been 

 electrified in the same degree, they 

 cease at once to exhibit any signs of 

 electricity, as if the electricities of both 

 were suddenly annihilated by their 

 mutual communication. Thus there 

 appears to be two different, and, in 

 some respects, opposite kinds of elec- 

 tricities ; the one obtained from glass, 

 the other from sealing-wax. Du Fay, 

 by whom this distinction was first no- 

 ticed, denominated the former the vi- 

 treous, and the latter the resinous elec- 

 tricity. 



(30.) The mode of action which these 

 two electricities exert on matter, may 

 be expressed by the following law : 

 namely, that bodies charged with either 

 species of electricity, repel bodies charged 

 with the same species, but attract bodies 

 charged with the other species; and that, 

 at equal distances, the attractive power 

 in the one case is exactly equal to the 

 repulsive power in the other. 



Accordingly, if we wish to ascer- 

 tain what is the species of electricity 

 with which a given body is charged, 

 we have only to approach it to a 

 small insulated pith ball, which has 

 previously been touched either with 

 excited glass or with excited sealing- 

 wax. If the body in question repel it 

 in the former case, or attract it in the 

 latter, its electricity is vitreous ; if the 

 contrary happens, it is resinous. 



(31.) Although each of these two elec- 

 tricities, when taken separately, acts in 

 a manner precisely similar to the other, 



they nevertheless exhibit in all their rela- 

 tions to each other a marked contrariety 

 of nature. Hence they are naturally 

 viewed as agents having opposite quali- 

 ties, which completely neutralize one 

 another by combination. 



(32.) Another remarkable circum- 

 stance which characterizes these agents, 

 is, that the excitation of one species of 

 electricity is always accompanied by the 

 excitation of the other ; and both are 

 produced in equal degrees. Thus, when 

 glass is rubbed by silk, or flannel, just 

 as much resinous electricity is produced 

 in the silk, or flannel, as there is vitreous 

 electricity produced in the glass; and 

 whatever electrified bodies are repelled 

 by the one are attracted in the same 

 degree by the other. If one of the sub- 

 stances happen to be a conductor, and 

 be held in the hand, the whole of the 

 electricity which the friction excites in 

 it will disappear as soon as it is pro- 

 duced, from its escaping through the 

 body of the person holding it, and being 

 lost in the earth. But if the precaution 

 be taken of insulating the rubber, its 

 electricity will become manifest, and is 

 always found to be of the opposite spe- 

 cies to that which is excited in the body 

 which is rubbed. 



(33.) Since the two surfaces rubbed 

 acquire opposite electricities, it follows 

 as a consequence of the law above 

 stated, that they must attract one ano- 

 ther ; and this is found invariably to be 

 the case. If a white and a black ribbon 

 of two or three feet long, and perfectly 

 dry, be applied to each other by their 

 flat surfaces, and are then drawn re- 

 peatedly between the finger and thumb, 

 so as to rub against each other, they 

 will be found to adhere together, and if 

 pulled asunder at one end, will rush 

 together with great quickness. While 

 united they exhibit no sign of electricity, 

 because the operation of the one is just 

 the reverse of that of the other, and 

 their power is neutralized and inopera- 

 tive. If completely separated, how- 

 ever, each will manifest a strong elec- 

 trical power, the one attracting those 

 bodies which the other repels. 



(34.) The very act of separation is 

 accompanied by appearances which in- 

 dicate that considerable portions of the 

 electricities excited on each of the sur- 

 faces fly back to the opposite surface, 

 and by their union become as it were 

 extinguished or inoperative ; and it is 

 only the remaining quantities which 

 have adhered more tenaciously to the 



