Chemical Theory of Electricity and Magnetism. 61 



But the theory of the ingenious Dr. Franklin failed also in explaining 

 other phenomena of the coated jar; since if the positive electricity 

 accumulated on one side of the jar repelled the electricity from the 

 coating on the other side of it, so as to produce an electric vacuum; 

 why should it be so eager, when a communication is made by some 

 conducting body, to run into that vacuum by its attraction or gravi- 

 tation, which has been made by its repulsion; as thus it seems to be 

 violently attracted by the vacuum, from which it had previously re- 

 pelled a fluid similar to itself, which is not easily to be comprehended. 



3. There is another mode by which either vitreous or resinous 

 electric ether is capable of condensation; which consists in con- 

 tracting the volume, so as to diminish the surface of the electrised 

 body; as was ingeniously shown by Dr. Franklin's experiment of 

 electrising a silver tankard with a length of chain rolled up within it ; 

 and then drawing up the chain by a silk string, which weakened the 

 electric attraction of the tankard; which was strengthened again by 

 returning the chain into it; thus the condensation of an electrised 

 cloud is believed to condense the electric ether, which it contains, and 

 thus to occasion the lightning passing from one cloud to another, or 

 from a cloud into the earth. 



This experiment of the chain and tankard is said to succeed as well 

 with what is termed negative electricity in the theory of Dr. Franklin, 

 as with what is termed positive electricity ; but in that theory the nega- 

 tive electricity means a less quantity or total deprivation or vacuity of 

 that fluid; now to condense negative electricity by lowering the sus^ 

 pended chain into the tankard ought to make it less negative; whereas 

 in this experiment I am told it becomes more so, as appears by its. 

 stronger repulsion of cork balls suspended on silk strings, and pre- 

 viously electrised by rubbed sealing wax : and if the negative electricity 

 be believed to be a perfect vacuum of it, the condensation of a vacuum, 

 of electricity is totally incomprehensible ; and this experiment alone 

 seems to demonstrate the existence of two electric ethers. 



