270 Researches in the Theory and Calculus of Operations. 



bis) is in equilibrium with its opposite atom a', and they 

 are also each in equilibrium with the contiguous atoms of 

 the surrounding medium. When the cushion or rubber B, 

 is passed to and fro on the surface of the electric, as the 

 surface of the former is not a smooth but a finely granulated 

 surface, but still somewhat coarser than the surface of the 

 electric (or in some cases there may be a degree of chemical 

 affinity sufficient to beget a moderate action even between 

 two solid substances), the atom or point a of the electric is 

 alternately pressed and relieved by the little projections on 

 the face of the rubber (or equilibrated by the action of che- 

 mical affinity): it suffers a series of renewed compressions, 

 each followed by a reactive dilatation ; each compression of 

 a liberates a', which consequently dilates, but immediately 

 returns its reaction to balance the dilatation of a. Thus the 

 two renewed atomic forces a and a', which did mutually 

 equilibrate by their right and lefthand halves, and are there- 

 fore equivalent to a single atomic force in equilibrium with 

 itself, are now alternately transported from the right to the 

 left surface of the electric, alternately unequilibrated and 

 again restored to equilibrium, so long as the electric and 

 rubber are both isolated; but if R, the latter be put in com- 

 munication with the earth G by means of a conducting wire 

 5, the cushion and earth together contribute one member 

 of the machine. "When the atomic force a leaves the cushion 

 and enters the electric, its place on the surface of R next 

 to E is supplied from the infinite reservoir of force G through 

 the conductor s, and the liberated force a' is now balanced 

 in its position on the left surface of E by the contempora- 

 neous arrival of the new equal force a on the right surface. 

 A second and every succeeding renewal of the frictional or 

 exciting pressure sends across an additional force a\ all 

 being held to the lefthand surface by the continued arrivals 

 from G; and thus a quantity of electric force will accumu- 

 late upon the surface of the electric, and may be transferred 



