100 Mr. J. P. Joule on the Electric Origin 



boiled out. I then removed the lamp, and immediately placed 

 in the mouth of the flask a cork, through which a small piece 

 of platinized silver and a stout iron wire had been passed. On 

 connecting the metals with the galvomometer (5.) its needle 

 was deflected to 32|°, and on shaking the flask very briskly it 

 could not be made to advance further than to S^°. This ad- 

 vance, slight as it is, was probably entirely occasioned by air, 

 which, notwithstanding my precautions, had found its way 

 into the upper part of the flask. 



8. The phasnomena originated entirely from the platinized 

 silver; and although a slight advance of the needle was some- 

 times produced by agitating the iron, it was not difficult to see 

 that the real cause was the propulsion thereby occasioned of 

 the aerated liquid against the negative* element, for when this 

 was avoided no advance of the needle could be produced by 

 agitating the positive metal. 



9. I thought it probable that an increase of the intensity 

 of the current would be produced by directing a stream of 

 oxygen gas against the negative element. On making the ex- 

 periment, I found that the needle advanced a ie\w degrees, 

 and that the same effect could be produced by a stream of hy- 

 drogen. There could be no doubt that the increase of inten- 

 sity arose rather from the agitation of the liquid than from any 

 specific action of the gases, and that this experiment was essen- 

 tially the same as that described in (5.). 



10. I impregnated some dilute sulphuric acid with a very 

 small quantity of oxygen, according to Thenard's process, and 

 then immersed into it a plate of platinized silver and a rod of 

 iron, both properly communicated with the galvanometer. The 

 needle stood for the first k\\ seconds at 68^ ; in three minutes 

 it declined to 50° ; in five minutes more to 49°, and in another 

 five minutes to 481^°. On agitating the platinized silver so as 

 to bring it repeatedly in contact with the yet undecomposed 

 deutoxide of hydrogen, the needle advanced to above 60°^ 

 The same pair, immersed in common acid, would have de- 

 flected the needle no further than 29° or 30°. 



11. The effect of the presence of oxygen at the negative 

 element is well observed by making it, in water, the positive 

 electrode of a voltaic battery. By this means oxygen is depo- 

 sited on its surface, and is there ready to produce an extraor- 

 dinary intensity. This deposit of oxygen is in fact the cause 

 of the action of Ritter's secondary' piles. 



12. The following was also a very convenient method of 



• To avoid misconception, it is perhaps as well to observe that I call 

 those elements of tiie voltaic battery negative, which attract or combine with 

 those bodies which are called "positively electrical," or "cations." 



