and its Effects. 9 



amber varnish, or a solution of shell-lac in alcohol ; thin wax- 

 paper, such as may be procured from apothecaries, and covered 

 with lac varnish. When rigidity, which these preparations pos- 

 sess only in a small degree, is not required, they are fully capable 

 of replacing mica. 



I have prepared many such paper condensers, some containing 

 54, others 30 square inches of covered surface. I have tested 

 them singly and in pairs, connecting them in the latter case by 

 a strip of tinfoil, and I have found that two together are not 

 more effective than one, and that even one of the smaller kind 

 was almost as effective as the great condenser of oiled silk. In 

 order to discover how far this diminution of the condensers 

 could be carried without injury to their actions, others were pi'e- 

 pared containing on each side 16, 9, 4, and 1 square inches of 

 covered sm-face ; some were made of varnished wax-paper, others 

 of gutta-percha, and others of oiled silk, upon which, owing to 

 their small size, the sheets of tinfoil could be easily and effectu- 

 ally fastened by means of shell-lac varnish. To my astonish- 

 ment, I found that all these small condensers, the smallest not 

 excepted, were, with respect to the length of the induction spark, 

 just as effective as the two great ones of oiled silk; at least the 

 differences were very irregular and very trifling, so that, without 

 difficulty, they could be ascribed to the changes which the parts 

 of the contact-breaker which hammer against one another suffer, 

 owing to the sparks which are produced between them. The 

 sole advantage which the great condensers possessed over the 

 small ones was, that the former produced less noisy sparks than 

 the latter. With the former, too, the sparks followed one another 

 more quickly when the distance between the poles approached 

 the limit at which the sparks can be obtained singly, or even at 

 all. On this account, therefore, the great condensers are not 

 superfluous, nor are they so for other reasons. First, all the 

 results mentioned were obtained with a current from one or from 

 two pairs of Grove's battery ; and the comparison of both cases 

 appeared to indicate, that, by employing a more intense galvanic 

 current (to which, however, I intentionally would not expose my 

 induction coil), the relation between the actions of the diffei'ent 

 condensers would change. Secondly, in the induction apparatus, 

 the action of the condensers is essentially influenced by the extra 

 current, i. e. the induction current which is produced in the 

 circuit of the inducing current itself, when it is broken. 



All that has hitherto been said applies only to the case where 

 this inner induction current is comparatively weak, consequently 

 to the case where the primary current traverses a comparatively 

 short and thick wire. If the former current is strengthened by 

 conducting the latter through a long and thin wire, without at 



