330 Prof. Bischof on the Temperatwe of 



metrical phenomena in the interior of the earth are totally inde- 

 pendent of all external circumstances, proves itself not only in 

 the earth's crust, but also in the depths of the sea and of lakes, 

 where a temperature prevails which is equally uninfluenced by 

 them. Quantities of water springing out of the earth at almost 

 every point, shew themselves equally independent of the influ- 

 ence of the external temperature, or at most but slightly modi- 

 fied by it. The object of this part of the present memoir will be 

 an investigation into these phenomena, and into the circumstances 

 more immediately connected with them, which may indirectly 

 lead us to the conclusion, that there exists in the interior of the 

 earth a tempesature which increases progressively with the depth. 



Chap. I. — On the Circumstances under which Wartn Springs are 

 found on the Surface of the Earthy and on their frequency of oc- 

 currence. 



If we were obliged to confine ourselves to those commonly 

 called warm or hot springs, it would be presumptuous to con- 

 clude from their temperature that of the interior of the earth in 

 general, as they are comparatively of rare occurrence ; but if we 

 be allowed to consider every spring as warm or thermal, whose 

 temperature exceeds, by however little, the mean temperature of 

 the place at which it rises, we shall find that thermal springs are 

 far from unfrequent. 



It may be considered almost as a general rule, that those 

 springs which are usually termed mineral springs exceed, more 

 or less, the mean temperature of the place, and it must be re- 

 garded as an exception when this is not the case. 



For several years I have been observing, at different seasons, 

 the temperature of about twenty mineral springs in the vicinity 

 of the Laacher See, and I find that even the coldest among 

 them always exceed the mean temperature of the place by near- 

 ly 1° R. (= 2i° Fahr.) Some of them even rise to 53°.375 F., 

 57°.875, and 58°.325,* and shew a constant degree of heat. The 

 warmest of the numerous mineral springs in the volcanic Eifel, 

 is that of the baths at Bcrtrich, the temperature of which is 

 OO^.S. The hot springs of Aix-la-Chapellc and Burtscheid 



* All the temperatures given in this article are reduced to the scale of Fah- 

 renheit. 



