366 Sir W. Snow Harris on the Laws and Operation [June 16, 



intensity being, by a well-established law of electrical force, as the square of 

 the quantity. 



8. These laws relating to charge, surface, intensity, &c., apply more 

 especially to continuous surfaces taken as a whole, and not to surfaces 

 divided into separated parts. The author illustrates this by examining the 

 result of an electrical accumulation upon a plane rectangular surface taken 

 as a whole, and the results of the same accumulation upon the same sur- 

 face divided into two equal and similar portions distant from each other, 

 and endeavours to show, that if as we increase the quantity we also increase 

 the surface and boundary, the intensity does not change. If three or more 

 separated equal spheres, for example, be charged with three or more equal 

 quantities, and be each placed in separate connexion with the electrometer, 

 the intensity of the whole is not greater than the intensity of one of the parts. 

 A similar result ensues in charging any united number of equal and similar 

 electrical jars. A battery of five equal and similar jars, for example, charged 

 with a given quantity = 1, has the same intensity as a battery of ten equal 

 and similar jars charged with quantity =2; so that the intensity of the 

 ten jars taken together is no greater than the intensity of one of the jars 

 taken singly. In accumulating a double quantity upon a given surface 

 divided into two equal and separate parts, the boundaries of each being 

 the same, the intensity varies inversely as the square of the surface. Hence 

 two separate equal parts can receive, taken together under the same electro- 

 meter indication, twice the quantity which either can receive alone, in 

 which case the charge varies w^ith the surface. Thus if a given quantity be 

 disposed upon two equal and similar jars instead of upon one of the jars 

 only, the intensity upon the two jars will be only one-fourth the intensity 

 of one of them, since the intensity in this case varies with the square of the 

 surface inversely, whilst the quantity upon the two jars under the same 

 electrometer indication will be double the quantity upon one of them only ; 

 in which case the charge varies with the surface, the intensity being con- 

 stant. If therefore as we increase the number of equal and similar jars 

 we also increase the quantity, the intensity remains the same, and the 

 charge will increase with the number of jars. Taking a given surface 

 therefore in equal and divided parts, as for example four equal and similar 

 electrical jars, the intensity is found to vary with the square of the quantity 

 directly (the number of jars remaining the same), and with the square of 

 the surface inversely (the number of jars being increased or diminished) ; 

 hence the charge will vary as the square of the quantity divided by the 

 square of the surface ; and we have, calling C the charge, Q the quantity, 



Q2 



and S the surface, C=^ ; which formula fully represents the phenomenon 



of a constant intensity, attendant upon the charging of equal separated sur- 

 faces with quantities increasing as the surfaces ; as in the case of charging 

 an increasing number of equal electrical jars. Cases, however, may possibly 

 arise in which the intensity varies inversely with the surface, and not in- 



