Temperature of Springs. 33 



the temperature of the Carlsbad water was formerly no higher 

 than at present *. On the other hand, the atmospheric water 

 imbibed by the earth may be heated at great depths by a high 

 temperature existing there, so that it may reach the glowing 

 masses much warmer than ll"R., which we have assumed. 

 But we cannot comprehend in our estimate all these possible 

 cases ; it is sufficient that we have got an approximation. We 

 may easily, at pleasure, increase or diminish the results, and in- 

 quire whether we are at liberty to assume the existence of such 

 masses of basalt, or other rocks, in a half-melted state, or even 

 at a white heat, in the interior of the earth ? This much can- 

 not be doubted, that, when we keep in view the immense masses 

 of volcanic mountains which we find on the surface of the earth, 

 and which we must admit have at one time been melted in its 

 interior, from which they were projected, that even much larger 

 masses of volcanic rocks may now exist in the interior of the Bo- 

 hemian Mittelgebirge, and other volcanic ridges, in a melted, or, 

 at least, in a glowing condition ? And, if even a part of their 

 warmth should be abstracted from such glowing masses by the 

 surrounding mountains, nothing prevents us supposing, that, in 

 such an event, warmth enough should still remain for the heat- 

 ing of the water. But this conducting power of heat can hardly 

 be very considerable, even for a period of a thousand years ; 

 for our forges, which frequently go throughout the whole year, 

 do not require a very thick wall of stone to confine much of the 

 heat. And then we must look at the weak conducting power of 

 volcanic products, which the following will prove. Monticelli 

 and Covelli found, on the 15th January 1822, in a crater of 

 Vesuvius, which vomited fire, a layer of snow, one foot thick, 

 which had fallen two days before -f-. They could even touch 

 with the hand the outside of the edge of a canal formed of con- 

 gealed lava, in which the glowing rock was still flowing J. 



Now, although, as shewn from the preceding calculations and 

 observations, the possibility of the heat of hot springs being de- 



" Compare Von Hoff", p. in art. 35. 



t Of Vesuvius in its activity during the years 1821, 1822, 1823, &c. from 

 the Italian, by Noggerath and Tauls, 1824, p. 15. 

 * Idem, p. 3?, and Noggeratli's Observations, p. 39. 



OCTOBER DECKMBER 1829. C 



