Hot and Thermal Springs. 273 



does not occur till we reach the regions where the mean tem- 

 perature is several degrees below 32°, or where the maximum 

 temperature of the soil is 32°. 



I have determined the temperature of the soil at the depth 

 of 12 inches, at four elevated spots in the Swiss Alps ; and in 

 the following table I have added to the results which I obtain- 

 ed, the mean temperatures of the places, calculated upon the 

 principle above established, viz. that the mean temperature is 

 32° at a mean height of 61 Q5 feet. 



At places in low situations, as Stockholm, Abbotshall, and 

 Brussels, the maximum temperature of the soil at the depth of 

 one foot takes place in July. But if, as my observations on 



" In a cleft in the rock the temperature, as low down as I could reach with 

 my arm, was 40°.55, and the same was at a depth of 12 inches in the ground 

 in a place exposed to the full power of the sun, I found a temperature of 

 41°.45. If the temperature of the numerous fresh-water springs which rise 

 in that neighbourhood (Chap. IV.) give the true mean temperature of the 

 soil, this must be -(-37°.40. But these springs which rise out of the much- 

 fissured rocks of limestone are probably thermal (Chap. I.), even though they 

 proceed from the Daubeiisee (Chap. XI.) 



t According to Michaelis (Frobel und Heer, p. 272) 7049 feet; accord- 

 ing to others 6953 to 71C0 feet. 



^ This is the mean of eighteen observations on the summit of the moun- 

 tain, which were made every half-hour from 9^ a. m. till 6J p. m., and at 

 5J A. M. of the 31st August. The maximum was 35°.C0, and the minimum 

 35M5. V 



II This is the mean of the observations which were made at the same time 

 as the others, but 40 feet below the summit on the southern declivity of the 

 mountain. The maximum was 37°.40, the minimum 36°.27. Both series of 

 observations were made at a time when the Faulhorn had been already some 

 days covered with snow one foot deep. The places where the observations 

 were made were, however, freed from the snow. 



