aiid its Effects. 129 



the positive or platinum pole, the first only will wear away ; and 

 on the plate of the tongue an eminence of fased platinum will 

 be formed, so that in time the platinum end of the hammer and 

 the toncjue touch one another. I always adopted this kind of 

 connexion, because it is much easier to replace the platinum end 

 and file the eminence down, than to fill up the holes which, in 

 the opposite case, would be burnt into the plate. 



Fizeau has already remarked, that the condenser may, to a 

 certain extent, be replaced by a wire of sufiicient intensity con- 

 necting the vibrating parts of the hammer. I have tested this 

 substitute and foimd it to be but an imperfect one, probably 

 because the circuit always remains closed. On this account I 

 was led to the construction of the hammer before described, by 

 means of which the interruptions of the current can be effected 

 within a liquid. In order to study the action of this instru- 

 ment, several liquids of very difi"erent conducting powers were 

 employed, — dilute sulplmric acid, spring water, alcohol of 0'863 

 spec, grav., and oil of turpentine. With sulphuric acid the instru- 

 ment had no strengthening influence whatever upon the induc- 

 tion current, and tliat clearly on account of its great conducti- 

 bility, which had also the effect of producing a copious decom- 

 position of water even when only a single Grove's element was 

 employed, and thereby causing hydrogen, in accordance with the 

 direction of the current, to be liberated at the pin in connexion 

 with the zinc. With oil of turpentine it had also no eff'ect, and 

 evidently for an opposite reason, viz. the complete absence of 

 conductibility. On the contrary, with alcohol, with spiring ivater, 

 and particularly with distilled water, the instrument had a strong 

 action, though still inferior to that of the condenser. It was 

 interesting to see how a single drop of water, placed between the 

 vibrating parts of the current-breaker, immediately caused a 

 vivid stream of sparks between the points of the discharger, 

 even when the distance between these points was so great, that, 

 without the drop, not a single spark would have appeared. 

 Water, alcohol, and oil of turpentine, however, all suffer decom- 

 position between the parts of the current-breaker. With water 

 this decomposition is electrolytic, with oil of turpentine it is 

 electro-thermic (so termed by me in a memoir published in 

 1847*), that is, it is produced by the heat of the interruption 

 spark ; and lastly, with alcohol the decomposition is a mixture 

 of both the fornuu-. 



The superiority of the condenser, when compared with any of 

 the above liquids, is best jji'ovcd by combining it with the cur- 

 rent-breaker when it is playing in water, alcohol, or oil of tur- 

 pentine ; a strong stream of sparks is immediately produced 

 * PoggendorfF's Annalev, vol. xciv. 



