Hot and Thermal Springs. 279 



from the last, which issued from a cleft in the rock among loose 

 blocks of stone, in a place which was difficult to be got at, and 

 this shewed 1°.85 to 1°.575 lower than No. 10. These three 

 springs rise out of the sandstone of the lignite formation, which 

 is there very much fissured. The comparatively higher tem- 

 peratures of No. 12 and 14 was no doubt occasioned by both 

 rising from a greater depth, and appearing in deep ravines. 

 The former evidently rises from a greater depth, as may be 

 seen by the motion of the sand at the bottom of the basin. 

 When springs rise in deep ravines from below, they must al- 

 ways appear with a temperature superior to the mean of the 

 place where they issue. All the rest of the springs either run 

 down directly through cracks in the rocks, or at least bear evi- 

 dent signs that they do not rise from below. 



If we take all these circumstances into consideration, and 

 compare the mean temperatures with the respective heights, it 

 becomes evident that these mountain springs are by no means 

 capable of giving the decrease of temperature in the soil with 

 the height. If, for instance, we compare the mean tempera- 

 ture of Nos. 3 and 18, we find that the scales of their annual 

 variations are nearly about the same ; it may, therefore, be sup- 

 posed that they both rise from about the same distance below 

 the surface. But, notwithstanding that they seem to be so pe- 

 culiarly adapted to the determination of the relative decrease 

 of height, yet when we come to examine into it we find it to be 

 exactly the contrary : for the decrease of temperature calculated 

 fi'om this mean is 2°.25 in 428 feet ; whereas the same decrease 

 is found, from the direct observations made near Bonn and on 

 the Lowenberg, to be 2°.25 in 683 feet. It is clear, then, 

 that the spring No. 18, which issues from a cleft in the 

 rock, brings down cold with it from above, and, therefore, does 

 not shew the temperature of the place where it makes its ap- 

 pearance. 



Although my endeavours to determine the decrease of tem- 

 perature with the height, from the mean temperatures of moun- 

 tain springs, have been unsuccessful, yet we see that the springs 

 in the valley of the Rhine, which lie at about the same level, 

 are very well adapted to the determination of the mean tem- 

 perature of the soil. It is true their mean temperature, 50°.22 



