10 Prof. J. C. Poggendorff on the Induction Apparatus 



amongst which were post-paper, covered on both sides with 

 the same time changing anything connected with the source of 

 electricity or the soft iron core, the action of all small condensers 

 considerably decreases, and that the more the smaller they are, 

 until in the smallest no action whatever is observable ; the great 

 condensers, however, retain their force undiminished. I con- 

 vinced myself of this by so combining the wires of the primary 

 coil as to cause the current, instead of traversing two wires side 

 by side, to traverse one after the other; therefore, instead of a 

 wire of double section and single length, one of single section 

 and double length was employed. The phsenomenon was still 

 more perceptible when the latter wire, which was now 1 millim. 

 thick and 200 feet long, was replaced by a wire f rds of a millim. 

 thick and 400 feet long, without changing anything else about 

 the apparatus. In both cases where the primary current was 

 comparatively weak, and the inner induction current compara- 

 tively strong, the condenser of 1 square inch surface, which was 

 before so effective, was now almost vidthout effect. 



Thirdly, the action of condensers depends essentially upon the 

 induction coils on which their influence is to be exerted. All the 

 results before mentioned were obtained with a very thin induc- 

 tion wire, 10,000 feet long ; when the thicker wire, 2400 feet 

 long, was employed, the small condensers again manifested a 

 very small action, and sometimes none whatever ; indeed, the 

 two smallest condensers appeared not only not to strengthen the 

 development of sparks between the poles of the induction coil, 

 but actually to weaken the same. This phaenomenon manifested 

 itself equally when the galvanic current traversed a short and 

 thick, or a long and thin wire. On the contrary, however, the 

 two large condensers of oiled silk still retained, in both cases, 

 their former energetic action ; indeed it was clearly perceptible 

 that the condenser 8 feet in length was superior to the one 

 2 feet long. 



Hence the stronger the galvanic battery, the longer and more 

 conducting the circuit of its current, and the thicker and more 

 moderate the induction wire ; in short, the more intense and 

 energetic the inner induction or extra current is made, the greater 

 the condenser must be in order to obtain an energetic develop- 

 ment of sparks between the poles of the apparatus*. When the 

 extra current is very intense, it passes through the condenser 

 the more easily the smaller its surface ; and from the sparks on 

 the current-breaker, it is easy to see that the actual outer induc- 

 tion current has an influence upon the weakening of the extra 



* I may also add, that the degree of insulation of the induction wire 

 api)eared to exercise an influence upon the action of the condenser ; this 

 action appeared to increase the more imperfect the insulation became. 



