WATSON'S ELECTRICAL THEORY. 535 



Watson's " sequel " is dated October 2Oth, 1746, and was 

 read before the Royal Society ten days later. Reduced to a 

 few words, his theory is simply that the exciting of an elec- 

 tric causes the advent thereto of fire from the nearest ad- 

 jacent conductor, and that the latter regains an amount 

 equal to that lost. " By asserting," he adds, "that that 

 we have hitherto called the effluvia does not proceed from 

 the glass or other electrics per se, I differ from Cabseus, 

 Digby, Gassendus, Brown, Descartes and the very great 

 names of the last as well as the present age." 



It may be conceded that Watson supposed that what he 

 calls the elastic electric ether became more dense in one 

 body and less dense in another; but it will be observed that 

 there is no principle of equilibrium here involved. He 

 imagined that the man touching the charged L,eyden jar 

 parted, immediately with his fire, and immediately re- 

 gained it from the floor. But no matter how highly 

 charged the jar, if, according to Watson's notion, he stood 

 on a pitch cake, or even had dry soles to his shoes, the flux 

 to him from the floor would thereby be prevented, and the 

 jar would give him no shock which is of course erroneous; 

 for the man's body, no matter on what it is supported, ob- 

 viously closes the circuit between the inside and outside 

 of the jar. 



Enough lias now been stated to show what Watson's 

 theory actually was in the fall of 1746. I shall recur to it 

 hereafter. 



The physical advance accomplished may now be noted. 

 Van Musschenbroeck had found, and Watson had likewise 

 recently re-verified the fact, that the thinner the glass of 

 the jar the stronger the shock. Watson alone had found 

 that the greater the area of the conductors in contact with 

 the glass, again the stronger the shock. Two of the three 

 conditions upon which depend the capacity of a condenser 

 had thus been discovered : namely, the thinness of the 

 dielectric stratum between the coatings, and the size of the 

 coatings themselves. The third (specific inductive capa- 

 city of the dielectric) was still far in the future. 



