422 EXPERIMENTAL INVESTIGATIONS. 



from the external air by a column of four feet four inches of 

 oil. The projecting extremities of the platinum wire were 

 now connected with the terminals of a voltaic battery and the 

 water heated by the wire ; some air was freed, and ascended 

 to the level of the tube this was made to escape by carefully 

 inverting the tube, so as not to let the oil mix with the water, 

 and the experiment continued. After a certain time the 

 boiling assumed an uniform character, not by such sudden 

 bursts as in the Florence flask experiment, but with larger 

 and more distinct bursts of ebullition than in its first boiling. 



The object of platinising the wire was to present more 

 points for the ebullition, and to prevent soubresauts as much 

 as possible. 



The experiment was continued for many hours, and, in some 

 repetitions of it, for days. After the boiling had assumed a 

 uniform character the progress of the vapour was carefully 

 watched, and as each burst of vapour condensed in the oil, 

 which was kept cool, it left a minute bead of gas, which 

 ascended through the oil to the bend of the tube : a bubble was 

 gradually formed here which did not seem at all absorbed by 

 the oil. This was analysed by a eudiometer, which I will 

 presently describe, and proved to be nitrogen. The beads of 

 gas, when viewed through a lens and micrometer scale at the 

 same height in the tube, appeared as nearly as may be of the 

 same size. No bubble of vapour was condensed completely, 

 or without leaving this residual bubble. The experiment was 

 frequently repeated, and continued until the water was so 

 nearly boiled away, that the oil, when disturbed by the boil- 

 ing, nearly touched the platinum wire ; here it was necessarily 

 stopped. 



To avoid any question about the boiling being by electri- 

 cal means, similar experiments were made with a tube, without 

 a platinum wire, closed at its extremity, and the boiling was 

 produced by a spirit-lamp. The effects were the same, but the 

 experiment was more difficult and imperfect, as the bursts of 

 vapour were more sudden, and the duration of the intervals 

 more irregular. 



The beads of gas were extremely minute, just visible to the 

 naked eye. I cannot find any record of their exact measure. 



