16 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XI.) 



less, and in the second instance greater than the original undivided charge. These 

 results are the more striking, as only one half of the interior of app. i. was modified, 

 and they show that the instruments are capable of bringing out differences in induc- 

 tive force from amongst the errors of experiment, when these differences are much 

 less than that produced by the alteration made in the present instance. 



^ iv. Induction in curved lines. 



1215. Amongst those results deduced from the molecular view of induction (1 166.), 

 which, being of a peculiar nature, are the best tests of the truth or error of the 

 theory, the expected action in curved lines is, I think, the most important at present ; 

 for, if shown to take place in an unexceptionable manner, I do not see how the old 

 theory of action at a distance and in straight lines can stand, or how the conclusion 

 that ordinary induction is an action of contiguous particles can be resisted. 



1216. There are many forms of old experiments which might be quoted as favour- 

 able to, and consistent with the view I have adopted. Such are most cases of elec- 

 tro-chemical decomposition, electrical brushes, auras, sparks, &c. ; but as these might 

 be considered equivocal evidence, inasmuch as they include a current and discharge, 

 (though they have long been to me indications of prior molecular action (1230.)) I 

 endeavoured to devise such experiments for first proofs as shouldnot include transfer, 

 but relate altogether to the pui'e simple inductive action of statical electricity. 



1217. It was also of importance to make these experiments in the simplest possible 

 manner, using not more than one insulating medium or dielectric at a time, lest dif- 

 ferences of slow conduction should produce effects which might erroneously be sup- 

 posed to result from induction in curved lines. It will be unnecessary to describe 

 the steps of the investigation minutely ; I will at once proceed to the simplest mode 

 of proving the facts, first in air and then in other insulating media. 



1218. A cylinder of solid shell-lac, 0*9 of an inch in diameter and seven inches in 

 length, was fixed upright in a wooden foot (fig. 3.) : it was made concave or cupped at 

 its upper extremity so that a brass ball or other small arrangement could stand upon 

 it. The upper half of the stem having been excited negatively by friction with warm 

 flannel, a brass ball, B, 1 inch in diameter, was placed on the top, and then the whole 

 arrangement examined by the carrier ball and Coulomb's electrometer (1180. &c.). 

 For this purpose the balls of the electrometer were charged positively to about 360°, 

 and then the carrier being applied to various parts of the ball B, the two were unin- 

 sulated whilst in contact or in position, then insulated*, separated, and the charge of 

 the carrier examined as to its nature and force. Its electricity was always positive, 

 and its force at the different positions «, h, c, d, &c. (figs. 3. and 4.) observed in suc- 

 cession, was as follows : 



* It can hardly be necessary for me to say here, that whatever general state the carrier ball acquired in any 

 place where it was uninsulated and then insulated, it retained on removal from that place, notwithstanding 

 that it might pass through other places that would have given to it, if uninsulated, a diflferent condition. 



