NATURAL PHILOSOPHY. 143 



main so for a minute, when another tumultuous ebullition would occur, 

 to be succeeded by a period of rest ; and the same phenomena would 

 be repeated at such regular intervals that the apparatus might almost 

 serve as an indicator of time. If a thermometer were placed in the 

 flask, it would be found that the temperature alternately rose and fell 

 some few degrees. Indeed, it could not be asserted that the boiling 



^3 ' 



point of water was constant, for it depended upon the amount of air in 

 solution ; and Mr. Grove believed that no one had yet succeeded in ob- 

 serving the boiling point of absolutely pure water. 



Mr. Grove suggested that the phenomena of the Geysers, or inter- 

 mittent explosive fountains of Iceland, would admit of a more satisfac- 

 tory explanation by reference to these facts than on the supposition of 

 the existence of complicated subterranean chambers. 



In the course of his experiments, Mr. Grove ascertained that it was 

 almost impossible to free water from gaseous bodies ; and, as a proof of 

 this, he cited the following experiment : A long glass tube closed at one 

 extremity, was bent in the middle to nearly a right angle ; the closed 

 limb was then half-filled with water, from which, by long boiling, the 

 air was supposed to have been expelled : the remaining space in the 

 tube was then completely filled with olive oil, and the open extremity 

 was dipped into a small basin of the same. Heat was then applied to 

 the tube until the water boiled, and this temperature was maintained 

 for a considerable time. Each bubble of steam which left the surface 

 of the water passed through the column of oil, becoming smaller and 

 smaller during its ascent ; but it never condensed without leaving a 

 microscopic bubble of gas, which at length accumulated to such an ex- 

 tent that it could be examined. It was found to consist of pure nitro- 

 gen ; and he had never succeeded in expelling the whole of this gas 

 from the water. The evaporation of nineteen-twentieths of the water 

 did not secure the remainder from being mixed with nitrogen. On 

 boiling ordinary water, air containing a slightly-increased proportion of 

 oxygen was first driven off, the oxygen gradually diminishing until pure , 

 nitrogen was expelled. The avidity with which such water again ab- 

 sorbs air is remarkable. In the expressive words of Mr. Grove, " it 

 sucks it up again almost as a sponge takes up water." By a slight 

 modification in the apparatus, the experiment was repeated with mer- 

 cury, instead of oil, in contact with the boiling water. It furnished a 

 similar result. 



A number of facts regarding the solubility of gas in water were 

 finally enumerated. The general conclusion drawn from the experi- 

 ments, was to the effect that water had a very powerful affinity for the 

 gases of the atmosphere ; that the oxygen could be eliminated by seve- 

 ral processes, but the nitrogen resisted all attempts to expel it from 

 solution ; so much so that it might be doubted whether .chemically pure 

 water (i. e., a compound of the two elements, oxygen and hydrogen, 

 only), had ever been prepared ; and, further, that ebullition (as applied 

 to water), under all circumstances, consisted merely in the production 

 and disengagement of bubbles of aqueous vapor, formed upon a nucleus 

 of permanent gas. The question, therefore, was raised as to whether 

 nitrogen is so absolutely inert a body as had formerly been supposed. 



