146 Influence of the connecting wires 



of different sizes are as their corresponding diameters, or sides, I think 

 we may safely conclude that the charges of these trial plates were as the 

 sides of a square of the same area, agreeable to what was said in [Art. 247]. 



285] 4thly. By Prop. XXXI [Art. 150] the charge of a cylinder whose 

 length = L and diameter = D is to that of a globe whose diameter = L 



2L dL 



in a ratio between that of i to log, -yr and that of 2 to log, ~ , and 



therefore the charges of the brass wire, long cylinder and short cylinder, 

 should be to that of the globe, supposing them to be connected with the 

 vial by which they were electrified by canals of incompressible fluid, in 

 a ratio between that of -894, -896 and -887 to i and that of 1-619, I- 573 

 and 1-469 to i. The observed charges are as -966, -980 and 1-028 to i, 

 which are between the two above-mentioned proportions, but approach 

 much nearer to the former than the latter, as might have been expected ; 

 so that the observed charges agree very well with the theory*. 



286] Sthly. If we suppose that the redundant fluid is disposed in the 

 same manner in a cylinder, whether the length is very great in respect 

 of the diameter or not, it is reasonable to suppose that the charges of the 

 brass wire, long cylinder and short cylinder, should be to each other in 

 a proportion not much different from that of -894, -896 and -887, or that 

 of -966, -968 and -959. The observed charges do not differ a great deal 

 from that ratio, only the charges of the two cylinders, especially the 

 shorter, are rather greater in proportion to that of the brass wire than 

 they ought [to be], so that according to this supposition the observed 

 charges do not agree exactly with computation. But if we suppose that 

 the redundant fluid is spread less uniformly in a cylinder whose length 

 is not very great in proportion to its diameter than in another, that is, 

 that there is a greater proportion of the redundant fluid lodged near the 

 extremities, which seems by no means an improbable supposition, the 

 observed charges may perhaps agree very well with what they should be 

 by theory, if they were connected by canals of incompressible fluid. 



287] With regard to the small disturbing causes mentioned in [Art. 

 277], as the length of the brass wire bears so great a proportion to its 

 distance from the trial plate and to its distance from the ground, it is 

 possible that its effect in increasing the deficiency of fluid in the trial plate 

 may be sensibly less, and also that the increase of charge, which it receives 

 itself from the ground near it being under-charged, may be sensibly 

 different from what it would be if it had been of a more compact shape, 

 so that perhaps some alterations may have been made in the experiments 

 by these two causes. I should imagine, however, that they could be but 

 small. It must be observed that the first of these two causes tends to make 

 the charge of the wire appear greater than it really was, and consequently 



* [Note 12, p. 382.] 



