354 Prof. Bischof on the Temperature of 



channels of springs from sand and stones raecbanically torn off or 

 borne along by the stream. Since hot springs and aqueous va- 

 pour are able to act very powerfully even upon hard rocks, 

 such, for instance, as marble, and thus to acquire quite a 

 muddy consistence, as I have observed in the Kaiserbad at Aix- 

 la-Chapelle, and in the baths at Burtscheid ; the channels of 

 springs may also in this manner become stopped up, especially 

 if the spring have a cementing property. 



Anglada supposes that the loss of heat, occasioned in the in- 

 ner strata of the earth, by warm springs, is not restored by the 

 power of conducting heat of the materials composing the interior 

 of the earth ; and that the strata must consequently suffer a gra- 

 dual diminution of temperature throughout the sphere of action 

 of those coolinor agents. 



A gradual diminution of the internal temperature of the 

 earth, caused by the loss of the heat carried off by thermal 

 springs, cannot be doubted, so long as that loss is not repaired 

 by any means. But whether that diminution has become per- 

 ceptible within historical times or not, is another question. 



The various degrees of temperature with which atmospheric 

 waters sink into the earth at different seasons of the year, 

 are already equalized in the uppermost strata of the earth's 

 crust ; for springs which rise from a moderate depth shew but a 

 trifling variation of temperature throughout the year, and that 

 of thermal waters is, in general, quite constant. The heat 

 carried by the pluvial waters into the earth, is, therefore, lost 

 in the almost inexhaustible provision of the earth's internal heat. 

 The waters having soaked through the earth's exterior crust 

 reach the strata, where the increase of temperature begins, with 

 a constant or nearly constant temperature. At this limit the 

 differencej between the temperature of the channels and that 

 of the waters can therefore only be infinitely small ; and as the 

 waters, by sinking through strata always increasing in tempera- 

 ture, become gradually warmer, it may be assumed that the dif- 

 ference is infinitely small in every point of their course. That 

 difference can only be perceptible when the waters do not filter 

 through the strata finely divided, but flow in considerable 

 streams. But the smaller the difference between the tempera- 

 ture of the waters and that of the channels through which they 



