352 Sir W. Snow Harris on a General Law of 



meter, containing about a square foot and a half of coating, as 

 A, tig. 8. 



18. The results of a series of experiments with six jars clearly 

 showed that the same quantity of electricity discharged from 

 several jars combined, has not so great a heating effect as when 

 discharged from a single jar, or from a less number ; the effect, 

 in fact, continued to diminish in some inverse ratio of the num- 

 ber of jars: this is, in fact, Prof. Riess's experiment. With a 

 view of ascertaining how far this result depended upon an exten- 

 sion of the battery in coated surface, I proceeded to charge a 

 single large jar, equal in surface to three or more of the first jars 

 taken together, and with the same quantity of electricity as at B, 

 fig. 8. Now in this case the battery was extended, not by a 

 divided, but by a continuous surface. The heating effect was now 

 the same as when the same quantity of electricity was discharged 

 from a single jar, not exposing above one-fourth the surface, as 

 already observed (10), notwithstanding that the relative "ten- 

 sions " or " densities " indicated by the electrometer were nearly 

 as 16 : 1. The result in question, therefore (17), as shown in 

 the experiment before quoted (11), could not possibly depend 

 upon any hypothetical change in the " density " of the accumu- 

 lated electricity, but must necessarily arise out of some disturb- 

 ing force tending to weaken the power of the current of discharge, 

 which distui'bing force could be no other than the resistance in- 

 troduced into the circuit by the extension of the battery in added 

 jars. It is quite impossible, as already observed (10), to extend 

 our battery in this way without at the same time increasing the 

 resistance to discharge by the added rods requisite to charge and 

 discharge the whole combination. And this resistance is still 

 further increased by the use of small metallic chains, often era- 

 ployed to transmit the electricity to the inner coating. 



19. Here it is also most important to observe, that in the 

 ordinary electrical battery there is always some resistance to 

 discharge, arising out of the translation, as it were, of the elec- 

 tricity accumulated on the surface of the glass to the coating, by 

 the conducting power of which the electricity is collected from 

 every point of the glass, and transmitted through the circuit of 

 discharge. Now in the common construction of the electrical 

 jar, the coating is never so closely applied to the glass as to be- 

 come as it were identified with it, and so effect this operation 

 perfectly. In the batteries as constructed by the old electricians, 

 a thin sheet of paper was often interposed between the coating 

 and the glass, with a view of avoiding fracture. In this case the 

 resistance to the free translation of the electricity through the 

 coating is remarkable. In the course of my experiments with 

 the jars of the battery before mentioned (16), I found one of the 



