492 Mr. Laming on the primary Forces of Electricity, 



pect that it niioht, like gravitation, be appreciable by a com- 

 mon balance; indeed the thought had then occurred, which 

 since I have found abundant reason to be satisfied with, that 

 the second electrical force was no other than the cause of 

 gravitation itself. 



15. To determine the nature of this electrical force, I there- 

 fore proposed to find in the case of a given body, first, whether 

 its tendency to approach the earth remains constant, while 

 the quantity of electricity in it is made to vary; and secondly, 

 if its tendency be not constant, whether it varies with the 

 quantity of electricity directly or inversely, and which of course 

 would depend on the nature of the force exerted by the elec- 

 trical atoms on one another. But any alteration in the quan- 

 tity of electricity natural to a body causes it to be attracted 

 by surrounding bodies ; and this attraction in respect to the 

 force to be investigated may be either an accelerating or a re- 

 tarding force; this attraction then, as well as the gravitating 

 force or weight of the body, requires to be so accurately coun- 

 terpoised, that there should be no tendency in it to motion in 

 any direction ; and this I accomplished by the following ar- 

 rangements. 



Experiment C. — Two circular plates twelve inches in dia- 

 meter were made of card-board and covered with tinfoil; one 

 was placed horizontally on an uninsulating support, and the 

 other suspended by fine silver wires above and about twenty 

 inches distant from it: by means of a micrometer screw this 

 distance could be increased or diminished with great nicety. 

 Midway between the plates was suspended, by a silk thread 

 attached to one of the arms of a balance, a sphere sixteen 

 inches in diameter, of caoutchouc covered with Dutch leaf, 

 and weighing about 1900 grains: the counterpoise at the op- 

 posite arm of the balance being partially immersed in water, 

 the index could be readily brought to zero, where it remained 

 very steadily. Under these circumstances, whenever the 

 sphere was charged, either positively or negatively, it became 

 attracted by both the plates with forces greater as their re- 

 spective distances were less. 



The sphere being kept constantly in a negative state, the 

 distance of the upper plate was so adjusted that the attraction 

 between these two was barely greater than the force in the 

 direction of the under plate ; a fact, which of course was 

 made known by a slight tendency in the sphere to ascend. 

 All other things remaining the same, the charge was then 

 changed to positive, when, in addition to the attraction of 

 the sphere by the two plates, there was also an increased 





