102 ELECTRICITY. 



tained by means of powerful magnets and delicate ap- 

 paratus. 



ELECTRICITY. 



244. FRICTIONAL ELECTRICITY. If a 



tional dectri- glass tube be rubbed with silk, it will after- 

 cit y ? ward attract to itself filaments of the silk, 



as a magnet attracts iron. Or, if the knuckle be ap- 

 proached to the tube, a spark may be drawn from it. 

 These phenomena are called electrical. Both glass and 

 silk are said to be electrically excited. The same ex- 

 periment may be made with a stick of sealing-wax. 



State the theory 245. THEORY OF ELECTRICITY. AcCOrd- 



of electricity. j D g to fa e v j ew CO mmonly entertained of 

 these phenomena, both glass and silk contain two electri- 

 cal fluids in a state of combination, which are so sepa- 

 rated by friction, that the positive fluid of both ac- 

 cumulates in the glass, and the negative in the silk. 

 The positive sustains the same relation to the negative, 

 that the north polarity of a magnet does to the south ; 

 and, in consequence of the difference of the separated 

 fluids, the two bodies containing them attract like op- 

 posite poles of a magnet. It is also true, that similarly 

 electrified bodies repel like similar poles of magnets. 

 As in the case of heat and light, we know nothing of 

 the electrical fluid, save by its effects. 

 Illustrate by ^46. The human body may also be elec- 

 examples. tricially excited, so as to yield a spark, by 

 rapid sliding over a carpet. Gas may be lighted by the 

 spark. The gas in certain manufactories is instantane- 



