Wb Prof. Biscbof 071 the Temperature of 



nearer their variations of temperature coincide with those of the 

 air, and conversely. The Table shews these diflferences to be 

 greatest, when the maximum temperature of the springs occurs 

 in July or August, and the minimum in January and February. 



In the Table we find that the difference between maximum 

 and minimum most frequently does not amount to 2°.25, and 

 that differences exceeding 11°,25 are of rare occurrence. I'he 

 greatest difference is 20°.25, with the exception of the springs of 

 Stuttgart and Tiibingen. As the temperature of these springs 

 was observed at the outlet of long aqueducts running at a very 

 small depth beneath the surface, it is evident that the tempera- 

 ture of the air must have had some effect upon it. So that, in 

 this respect, the differences of temperature of those springs can- 

 not serve for a comparison. 



A singular relation is observed to exist with regard to the 

 annual variations of temperature of the salt springs of Werl. 

 Tliey correspond almost exactly with the variations of tempera- 

 ture of the air, and yet the springs are undoubtedly thermal. 

 If these were produced in the same manner as the very copious 

 springs of the Jordan, Lippe, Pader, Heder, and so forth, which 

 rise on the western declivity of the Teutoburger Wald and the 

 Haar, it would be easy to conceive that their variations of tem- 

 perature should correspond with those of the air ; for those 

 springs are, in fact, rivers, which having sunk from higher re- 

 gions into the numerous clefts in the chalk rocks, pursue a sub- 

 terraneous course, and reappear at a much lower level. Such 

 considerable bodies of water, in sinking to a depth where the in- 

 crease of temperature towards the centre of the earth is percep- 

 tible, do not entirely lose the temperature which they had ac- 

 quired whilst running on the surface ; so that, notwithstanding 

 their appearance as thermal springs, the variations of the ex- 

 ternal temperature still shew themselves in them.* 



• Between the variations of temperature and of the contents of salt of these 

 springs no relation can be found. Their mean temperature in lfl33 was 

 higher than in 1832; whilst, on the other hand, the quantity of salt contain- 

 ed in them was much smaller. Besides, the maximum of salt contained in 

 them falls constantly in May, whilst the minimum has no determined period. 

 This circumstance indicates a very peculiar, or, I would say, a complicated 

 combination of the subterranean channels at Werl ; as does also the fact, that 

 different borings in that neighbourhood, often situated very near to each 

 other, yield sometimes strong salt- waters, and sometimes springs of iiesh- 

 irater. 



