♦8 Mr. Laming oti the primary Forces of Electricity. 



mosphere as the part of the charged body to which the con- 

 ductor is presented is smaller and more prominent. 



45. The form of the conductor, or of that part of a con- 

 ductor from which the phis charge is to be abstracted, being 

 given, then if an unit of quantity of free electricity be re- 

 tarded in it by an unit of minor force, two units of quantity 

 should be retarded by two units of force, three quantities by 

 three units of force; the retarding force thus continually in- 

 creasing in the simple ratio of the quantities of free electri- 

 city. Consequently the discharging distances from any given 

 surface should vary in the same ratio ; for, as we have already 

 seen, (10) the intensity of abstracting, or major force being 

 constant, the distances at which it acts var}' in this ratio. 



That this is the ratio observed by electrical discharges un- 

 der all circumstances may be proved by an appeal to facts ; 

 and I think the proof will be received as an additional evi- 

 dence of the minor electrical force. 



46. Electrical discharges, as they occur between conductors 

 compensated in the open atmosphere, have been examined 

 by Mr. Harris ; whose experiments on the subject decide most 

 unequivocably, that under such circumstances at least, and 

 whether the conductors be connected with Leyden surfaces 

 or not, " the quantities of electricity requisite to produce a 

 discharge vary with the distances directly*." 



47. Mr. Harris has also ascertained with his usual accuracy, 

 that in a rarified atmosphere " the distances through which a 

 given accumulation could discharge, varied in an inverse simple 

 ratio of the density of the air. Thus in air of one half the 

 density the discharge occurred at twice the distance f." Now 

 by reducing the density of a compensating atmosphere to one 

 half, we virtually double the charge to be compensated by the 

 residuum ; in this case also we therefore see that the dis- 

 charging distances are as the quantities of free electricity. 



48. The same acute philosopher has further proved, by a 

 very ingenious and exact mode of experimenting, that pro- 

 vided the densities or quantities of air in a receiver remain 

 unchanged, the temperatures may take a very wide range with- 

 out affecting the discharging distance of a given accumulation 

 of free electricity; in this case again the discharging distances 

 are therefore as the quantities of free electricity. 



49. The very great distances at which electrical discharges 

 may be made to take place in vessels nearly exhausted of air 

 has induced a general belief that, in the language of Dr. Ure, 

 *' electricity is confined to the surface of bodies by a species 



* Phil. Trans. 1834, p. 225. f Ibvi., p. 229. 



