$4i8 Prof. Bischof on the Temperature of 



springs is a phenomenon of very general occurrence, which mav 

 be traced through all formations, from the very youngest of the 

 stralified to the very oldest rocks, the chemical processes which 

 cause the heat of these waters must be equally universal. Or 

 is it, perhaps, less difficult to account for the heat of a spring 

 whose temperature only exceeds the mean temperature of the 

 place by a few degrees, than to find an explanation for the crea- 

 tion of those commonly called hot springs ? 



Anglada* adds another argument of no small weight against 

 the explanation of the heat of thermal springs by any chemical 

 process, namely, that it would be difficult to conceive how such 

 a process should continue in action for so long a time, and with 

 such uniformity as would be necessary to explain the uninter- 

 rupted course of the springs, their uniform productiveness, and 

 their unvarying temperature and composition. 



Since, then, we are obliged to admit that the conditions ne- 

 cessary for the production of warm springs must exist in all 

 parts of the earth, we find ourselves imperceptibly led to the 

 hypothesis of a superior temperature in the interior of the earth. 



Laplace already endeavoured to account for the heat of 

 thermal springs, and their uniformity within the memory of 

 man, by this internal heat of the earth.-f- Subsequently, it has 

 been shewn by Arago,| that the temperature of artesian wells 

 is higher the deeper they spring; and he has brought this for- 

 ward as a proof, that the temperature of the strata of the earth 

 increases constantly with the depth. Anglada,§ who is also led 

 to this hypothesis, thinks, that if the heat of mineral waters were 

 only caused by the increase of temperature towards the centre 

 of the earth, it would be contradicted by our not meeting every 



• M^moire pour servir "k I'Histoire, &c. vol. i. p. 15. 



-f- Annal. de Chim. et de Phys. vol. xiii. p. 415 — This philosopher says, 

 " Si Ton con9oit, que les eaux pluviales, en penetrant dans Tinterieur d'un pla- 

 teau eleve, rencontrent, dans leur mouvement, une cavite de trois mille metres 

 de profondeur, elles la rempliront d'abord ; ensuite, acquerant h cette pro- 

 fondeur, une chaleur de 100° au moins, et devenues, par \\ plus legeres, elles 

 s'eleveront, et seront rernplacees par les eaux superieures, en sorte, qu'il 

 s'e'tablira deux courans d'eau, Tun montant, I'autre descendant, perpetuelle- 

 ment entretenus par la chaleur int^rieure de la terre. Ces eaux en sortant 

 de la partie inf(t?rieure du plateau auront t^videmment une chaleur bien sup^- 

 rieure k celle de I'air au point de leur sortie." 



+ AnnaL de Chim. et de Piiys. vol. xxix. p. 317. § P. 17. 



