Hot and Thermal Springs. 157 



a greater yearly variation of temperature, must also be effected 

 by a greater instantaneous change of temperature. 



Those seas and lakes, which have a great depth immediately 

 near shore, will produce a depression of temperature on the shore, 

 in consequence of the low temperature at their bottom. So that, 

 if the mean temperature at a certain distance from the lake or 

 sea, where its cooling influence can no longer be felt, be f, the 

 chthonisothermal of f will bend downwards on approaching the 

 sea or lake. It would be interesting to discover the mean tem- 

 perature of the earth on the shores of deep lakes or seas, and at 

 various distances from them, in order by that means to ascertain 

 to what distance their cooling influence extends, and to deter- 

 mine the consequent curves of the chthonisothermal lines. For 

 want of such observations, continued as they should be for at 

 least a year, I made some solitary observations on the temperature 

 of the earth, at a depth of one foot, between the lakes of Thun 

 and Brienz, on the 1st Sept. 1835, from which I obtained the 

 following results : — 



Lake of Thtm, at its surface, close to the shore, near NevJiaits, 70.47 



at the bottom, at a depth of 15 inches, . . 64.85 



The Aar, where it falls into the lake, .... 66.0 

 The soil, temperature of the sand at the bottom of the lake, at 



the same spot, . . . . . . .58.10" 



The soil, at another spot near the shore, where the lake is very 



shallow, ....... 67.65© 



56.41 Sh. 



Mean 57-02 

 The soil, 230 paces from the lake towards Unterseen . . 61.92 



57.20 Sh. 



Mean 59.56 

 half-way between the lake and Unterseen, . . 62.37 



57.42 Sh. 



Mean 59.89 



&i Unterseen . . . . . .61.470 



58.55 Sh. 



Mean 60.01 



• The ol)servations marked were made in many j)lace.s exjjosed to the 

 rays of the sun ; those marked Sh,, on the otlier hand, were made in the shade 

 on the nortli side of Louses, w.ills, and so fortli. 



