Lesson I. 



; KICI n. 



133 



perfect non-conductors. Water and steam 



->d conductors, aud, therefore, uo 



can understand how it is that electrical 



I will not answer in damp 



he attr.osph.-re conducts 



it away.* Bat a dry atmosphere being a 



noo -conductor, it insul.. 



rub a metallic rod while 

 it is held in your lund, why does it not 

 become electric ? 



P. Because the electricity which is 

 >"d by friction is transmitted to the 



>ly. 



/'. Would it not be better to call 

 bodies by some other names than con- 

 doctors and non-conductors ? 



P. Vrs ; it would be more correct to 

 call them good and bad conductors. 



13. T. How maiiy kind? of electricity 



P. - Frictional electricity ; 



2. Galvanic or Voltaic electricity ; 3. 

 Theme-el 



I .M.i: >-; on : and 6. Electro- 

 low many kinds of fractional 



-, and 

 rtsinons or negative electricity. 



15. T. Prove that such is the case. 

 /'.Here is i.i . lulura. 



a plasR ! 



ich of 



i ball is supen<i< 

 of 3 f M<Iultim 



T1>U I* Impor'nn 

 berrd v 



and rare taken to . 



'.v warmth and frkt. 



n made electric by contact with a 

 glass rod rubbed with silk, and the other 

 by a rod of shell-lac rubbed with fur. 

 Now, observe what t.ikes ]>'. tee. When I 

 bring the shell-lac near to the ball that 

 has been repelled by the glass rod, it w ill 

 attract the ball. [Does so.] No 

 will see that the reverse takes place on the 

 other side. Places the glass rod near to 

 the ball.] \ouobserve that the ball re- 

 pelled by the shell-lac is attracted by the 

 have thus provid that the 

 electricity developed by glass is not iden- 

 tical with that evolved from resin, because 

 the one attracts and the other rep 



1 <> 7'. How are the terms positive and 

 negative expressed ? 



P. By the arithmetical sijrns of plus + 

 ami minus , the former denoting the 

 positive and the latter the negative elec- 

 tricity. 



17. 7". From what you have shown 

 me, it appears that certain phenomena 

 occur when substances that possess elec- 

 trical properties come in contact, or are 

 presented to each other. I'.xplaiu these 

 phenomena. 



/'. 15 xlus in dissimilar states of elec- 

 tricity attract each other; for exam; 

 anci - in simil ir 



each other ; for xaniple, when both 

 or both +. 'S are in an ordi- 



nary state, or uneitctrifu-d, t: 

 to be n - / ,/. 3 ) 



18. T. Does i. y depend in 



/'.Yes; smooth glass rubbed with 

 silk or wool becomes positive, but if it be 

 \ sand, it becomes 

 under the same tn atnu nt. 



QUESTIONS ON I.KSSUN I 

 1. Wh.it is n:- -dies being 



:il ? 



v peculiar about elec- 





 'rove that ti 



i li >\\ .in- bodii i <i; 



i 1 Of 



7. Ho .t : ooad -ions of 

 bodies expressed ? 



