GALVANISM. 35] 



This result, after all the precautions which had been taken, was quite unex- 

 pected, and, as may be imagined, gave not a little surprise to the experimenter. 

 Still he did not for a moment entertain any of the speculations of the genera- 

 tion of these substances in the water. His next step was to repeat the exper- 

 iment with glass instead of agate cups, using the same quantities of the same 

 water, and exposing them for the same time to the action of the same battery. 

 He argued, that if the cause lay in the water, the effects would be the same ; 

 but that if the cup.* had any share in producing them, they might be expected 

 to be different. The result confirmed his anticipation. The alkali was pro- 

 duced in the cup N in quantity twenty times as great as with the agate cups, 

 but there was no trace of the acid. The experiments were then repeated sev- 

 eral times with the agate cups, when the acid and alkali reappeared in quanti- 

 ties, which, when compared with each other and with the result of the experi- 

 ment with glass cu[.s, left no doubt that the agate cups themselves had been 

 the chief if not the only source of the acid, and, in a considerable degree, of 

 the alkali also. Still it was impossible to ascribe the effects altogether to the 

 material of the cups ; and he was impressed with the suspicion that the writer 

 itself, notwithstanding its careful distillation, must have held more or less alka- 

 line matter in solution. It was known that the usual tests would fail to indi- 

 cate the presence of alkaline impurities when their proportion in water was 

 under a certain limit ; and the New river water, which he used, contained an- 

 imal and vegetable impurities, which might furnish neutral salts capable of be- 

 ng carried over in the process of distillation. 



The agate cups were now replaced by two conical cups of pure gold (fig. 4), 



Fig. 4. 



each containing about twenty-five grains of water. Distilled water in these 

 was exposed to the action of a battery of 100 pairs of six-inch plate% Ih ten 

 minutes indications of acid and alkali were formed in the cups D and N re- 

 spectively. The process was continued for fourteen hours, during the whole 

 of which time the acid increased in the cup D. The same increase was not, 

 however, observed in the alkali in the cup N ; on the contrary, it reached its 

 maximum state in a short time, and continued without increase afterward. On 

 heating the cup N, the alkali diminished, but could not be altogether dismissed. 

 These experiments being repeated with similar results, it became apparent 

 that the source of the acid and alkali must exist in the water itself, and must 

 either have arisen from saline matter remaining in solution in the water after 

 distillation, or have been produced by the azote, which exists in minute por- 

 ? lions in all water exposed to the air. The latter supposition would not be in- 

 S compatible with the circumstance of the alkali speedily attaining & maximum, 

 ? since the continued absorption of azote from the atmosphere by the water would 

 i be stopped when the latter would become charged with hydrogen. 



The former supposition was adopted, and it was determined to submit the 

 ) water which had been used in the last experiments to slow redistillation. A 



