Hot and Thermal Springs. 



From all these experiments it follows, that the heat of acidu- 

 lous springs cannot be ascribed to the carbonic acid gas itself, 

 but principally. to the aqueous vapours which accompany it, for, 

 as Von Buch imagines the production of acidulous springs, the 

 vapours of water must also assist in raising their temperature. 

 Besides, this hypothesis presupposes the existence of an elevated 

 temperature below the origin of these springs ; so that we need 

 only suppose them to descend into the vicinity of those hot 

 springs, and they will acquire an elevation of temperature, inde- 

 pendently of the inconsiderable increase caused by the absorption 

 of the carbonic acid gas. 



If the rising of springs follows the laws of hydrostatics, it is 

 easy to conceive how carbonic acid gas and aqueous vapours 

 should find their way into the channels through which they flow. 

 I have made several experiments on this subject.* I connected 

 two glass-tubes, each of four feet long, by a brass pipe, in such 

 a manner as to form an inverted syphon. At the side of the 

 brass tube, another tube was fixed at right angles to it, having 

 a cock in it, the opening of which was very narrow ; to this was 

 luted a small tubulated retort. When the cock was shut the 

 apparatus formed an uninterrupted syphon ; and even when it 

 was open, the water continued to flow out of the shorter tube, so 

 long as it continued to be poured into the longer one ; for the 

 air in the retort was only compressed, without its being able, on 

 account of the smallness of the aperture, to escape through the 

 cock, and let in the water in its place. When carbonic acid gas 

 was generated in the retort, and the cock opened, the gas rose 

 through the water in the shorter tube in separate bubbles, and 

 escaped from the water collected in a small basin fixed on the 

 top of that tube. During the evolution of the gas in this appa- 

 ratus, which is a true representation of the course of a mineral 

 spring, the water flowed without interruption out of the basin. 

 Now, as, under these circumstances, where each bubble of gas 

 entirely filled up the channel, and, at the moment of its escape, 

 caused an interruption in the course of the water, there was no 

 perceptible interruption in the flowing off^, still less can such an 

 interruption take place in nature, where the bubbles must cer- 

 tainly very seldom fill up the channels through which they pass. 

 • Poggendorflf 's Annal. vol. xxxii. p. 261. 



