131< Prof. Bischoff on the Temperature of 



ber 1831, the temperature varied from 56°.80 to 62°.37, giving a 

 difference of 6.07. This circumstance can hardly be accounted 

 for in any other manner, than by supposing colder springs to exist 

 there, which suddenly cool the warmer waters rising from below. 

 The mixing of these springs cannot take place immediately, as 

 the sounding well is lined with a sheet-iron tube to the depth 

 of 621 feet. A later observation gave this sudden increase, 

 between 200 and 250 feet at 5.85 ; indeed the temperature was 

 found to be generally lower at equal depths at the time of this 

 experiment, than during the former. The highest tempera- 

 ture at the bottom of the well was 74.30.* 



Were a well to be sunk on Teneriffe, for the sake of ther- 

 mometrical observation, at less than 4000 feet above the level 

 of the sea, within which limit Von Buch found but slight va- 

 riations of temperature in the springs, would not such an uni- 

 form temperature in the waters issuing forth at such unequal 

 elevations, have some influence on the temperature of the strata 

 situated within those limits ? 



Chap. XIII. — What influence have thermal springs on tJie tempe- 

 rature of the interior of the earth 9 



In Chap. IV. it has been observed, that considerable bodies 

 of water rising with an elevated temperature are capable of in- 

 fluencing the temperature of the soil. This remark holds 

 equally good for strata situated at a greater depth. W^ere we 

 obliged to confine ourselves to the , consideration of those 

 commonly called warm or hot springs, it might be objected 

 that they are a local phenomenon, and ought, therefore, not to 

 be taken into account. But in Chap. I. we have shewn that 

 thermal springs are of very general occurrence ; that they are 

 not entirely wanting in any formation ; and that in different 

 places they are only more or less frequent, and more or less 

 elevated above the mean temperature of the air, sometimes rising 

 to the surface by natural or artificial artesian wells, and some- 

 times being held back by impervious strata. How various and 



* Poggend. Ann. vol. xxxiii. p. 233. See also vol. xxii. p. 136, and in the 

 '* Schrii'ten der Berliner Akademie" for 1831. 



