concerned in the Phenomena of ordinary Electricity, §c. 337 



same instant; and then, by the reunion, the former intensity 

 would be changed into a new one, which would be determined 

 by the diameter of the wire constituting the coil, and its more or 

 less perfect insulation. Hence the number of jars that contains 

 the charge is of little consequence, when the whole electricity 

 contained in them must be reunited in the galvanometer wire ; 

 be the number of jars what it may, the intensity in the coil will 

 be the same so long as the total quantity is the same, and there- 

 fore the deflection will be the same. 



The case is similar to that of the common experiment of melt- 

 ing an iron wire by the discharge of a Leyden battery. If the 

 battery contain the quantity of electricity adequate to melt a 

 certain length of the wire, it matters not whether the charge be 

 contained in one jar, or ten, or one hundred. When the discharge 

 takes place, the contents of all the jars will pass through the 

 wire at the same instant, in the same degree of concentration as 

 if the whole charge had been confined in one jar only ; and the 

 fusion of the same length of wire will as certainly follow in all 

 cases. I take no account of a little waste which the connecting 

 rods of the jars would cause. 



Professor Faraday now charged the fifteen jars of the battery, 

 not as before with thirty turns of the plate-machine, but with 

 fifty; and made the discharge, sometimes with a mere wet 

 thread, sometimes through 38 inches of thin string wet with 

 distilled water, and sometimes through a string of twelve times 

 the thickness, 12 inches in length, and soaked in dilute acid. 

 The intensity of the current constituting the discharge must 

 have varied, as he conceives, extremely in these several cases ; 

 and yet the deflection was " sensibly the same in all of them*." 



In this experiment, so different in aspect yet so similar in 

 results, there appears to be no real additional evidence in favour 

 of the law deduced. In the first place, it is to be remembered 

 that the greatest deflection of the needle in Colladon's experi- 

 ments was 10°, and in Faraday's 4-1°. These deflections seem 

 to have been produced by the maximum quantity of electricity 

 which these particular galvanometer coils were capable of insu- 

 lating ; for the wire of the coil will not conduct, through its 

 whole length, any quantity of common electricity which we 

 choose to present to it. M. Colladon observes, that "electricity 

 of great tension easily passes from one turn to another across the 

 silk which separates themf-" In proof of this, he found that by 

 transmitting a current of electricity from a Nairne's machine, or 

 a plate-machine of 5 feet diameter, through a Nobili's galvano- 

 meter, the deviation did not exceed 3° or 4°. But on employing a 



* Researches, par. S66. 



t Annates de Ckimie et tie Physique, vol. xxxiii. j>. 67. 

 Phil. Mag. S. 1, Vol. 3. No. 19. May 1852. Z 



