Hot and Thermal Springs. 34l 



as the spring rises to the surface, when the gas disengages itself 

 again, and, as is so often the case with ricli carbonated springs, 

 issues forth in uninterrupted streams. 



The evohuion of carbonic acid gas from acidulous springs, 

 which is in some cases so enormous, might perhaps lead us to 

 conjecture, that it for the most part proceeds from streams of 

 gas, which come up from the interior without having yet been 

 absorbed by water. But I have found, by measuring the quan- 

 tity of carbonic acid gas and water yielded in a certain time by 

 one of the richest carbonated springs, that the gas evolved, and 

 that which was absorbed by the water, together, only made up 

 5.3 limes the volume of the water.* 



Supposing, then, that this gas came in contact with the water 

 at a depth of only 170 feet, the hydrostatic pressure which would 

 be there exerted, would be sufficient to cause the absorption of 5.3 

 times the volume of the water. But this spring, bearing a tem- 

 perature of 9° above the mean temperature of the place, cer- 

 tainly rises from a much greater depth. The supposition, there- 

 fore, that a great quantity of heated carbonic acid gas could 

 assist in the elevation of the temperature of a spring, by passing 

 through its channels, is proved to be unfounded. 



It appears from observations made on the Mofettas, which 

 usually succeed great eruptions of Vesuvius, that carbonic acid 

 gas evolved, according to Von Buch's hypothesis, cannot possibly 

 have a temperature equal to that of r rbonic acid gas disengaged 

 from chalk submitted to a red-heat i. a gun barrel. Thus Mon- 

 ticelli and Covellij found, that cavities filled with the mofettas, 

 were only 3°.85 warmer than those in which no mofettas existed. 

 If, then, streams of carbonic acid gas, issuing forth so near their 

 volcanic origin as these do, shew so low a degree of heat, it can- 

 not be expected that such as rise in the neighbourhood of ex- 

 tinct volcanic action should be warmer. Nor have I observed 

 a superior temperature in any which I have examined of the 

 numerous exhalations of carbonic acid gas which occur in the 



• Poggend. Ann. vol. xxxii. p. 251. 



+ Storia de Fcnomeni del Vesuvio, avvenuti negli anni 1821, 1822, e purle 

 del 1823, con observazioni c sperimenti di T. Monticelli e N. CovellL Na* 

 poli, 1023. Translated into German by Nojgerath and Pauls. Elberield, 

 1824, p. 19.3. 



VOL. XX. KO. XL. APRIL 183G. S 



