NOTES ON THE TWO ELECTRICITIES. 29 



electrical machine is derived from the ground, and 

 not from the machine itself; also in some of our 

 standard works on chemistry, as well as those on 

 electricity, the same opinion obtains. Thus in Stur- 

 geon's lectures on electricity, the following state- 

 ments are made : " When the cushion is in metallic 

 connection with the ground by means of the copper 

 wire, or when the hand is placed on it, it gets an 

 abundant supply from that source." Again, " I have 

 already stated in a former lecture, that the insulated 

 cushion or rubber of a machine yields but a small 

 portion to the revolving glass, because of a want of 

 supply from the ground." Also in one of our 

 standard works on chemistry, it is there stated " that 

 when one conductor is un-insulated, the electricity 

 derived from the other is proportionably augmented ; 

 in the positive conductor, because then the other 

 draws uninterrupted supplies from the earth." 



38. The following experiment proves that this 

 opinion is erroneous. 



To the ball of the prime conductor of an electric 

 machine I presented an insulated conductor B, one 

 of the extremities of which terminated in a metallic 

 ball, and was placed within less than an inch of the 

 ball of the prime conductor. The other extremity 

 terminated in numerous points or needles. A similar 



