204 Prof. J. C. Poggendorff on the Induction Jpparatm 



As a general result of tliis comparison, it was quite evident 

 that the action of the sparks of the induction coil was in all cases 

 quite as strcJng when t/ie hammer worked in a vacuum without the 

 condenser, as ivhen it worked in air ivith a condenser; in some 

 cases, indeed, it was considerably stronger. 



This was particularly the case with the thicker and shorter 

 induction wire, when the wires of the primary coil were at the 

 same time connected side by side, so as to form a wire 100 feet 

 long and \^2 millims. in diameter. 



When the wires of the primary coil were connected in this 

 manner, the combination of the condenser with the hammer in 

 a vacuum had apparently no influence upon the spark-distance 

 of the induction coil, at least no increasing influence ; the sparks 

 were mei'cly stronger sometimes. On the contrary, when the 

 primary wires were connected one after the other, so as to form 

 a wire 200 feet long and 1 millim. in diameter, the combination 

 of the hammer and oiled-silk condenser considerably diminished 

 the spark-distance; a phsenomenon which at first sight appeared 

 strange. At the same time, however, a continual crackling could 

 be heai'd in the condenser. The remarkable phcenomenon, there- 

 fore, was caused by the extra current, owing to its increased in- 

 tensity, penetrating the condenser in the form of sparks*. 



The luminous phsenomena of the induction current in the 

 electric egg are also very well developed when the hammer vi- 

 brates in a vacuum without the condenser ; apparently just as 

 well as when the hammer works in air, and is connected with 

 the condenser. It is here of importance to what degree the 

 rarefaction is carried ; if it amounts to about 1 line of mercury 

 pressure, and at the same time a great intensity is given to the 

 current by developing it in a wire 10,000 feet long, the combi- 

 nation of the condenser with the hammer vibrating in a vacuum 

 is without influence upon the phsenomenon ; in the opposite case 

 it increases the phfenomenon in the same manner as when, at a 

 former timefj the hammer played in fi-ec air. 



With reference to the cause of the action of the hammer in a 

 vacuum, I will only remark that it appears to me to be of the 

 same nature as that of the condenser. 



The vibrations of the hammer in a vacuum are very interesting 

 and instructive in the study of the extra current which is deve- 

 loped in the proper circuit of the galvanic current, partly by the 



* The condenser is of course perforated by this, so that I have always 

 (liscoutiuued the experiment after a very short time. Small lioles, liowever, 

 appear to injure the action of the condenser but little, if at all, 



t Phil. Mag. vol. X. p. 127. 



