244 THERMAL SPRINGS. SKCT. XXVI. 



crease cannot be obtained in this manner. Perhaps the 

 most satisfactory experiments on record are those made 

 by MM. August de la Rive and F. Marcet during the 

 year 1833, in a boring for water about a league from 

 Geneva, at a place 318 feet above the level of the lake. 

 The depth of the bore was 727 feet, and the diameter 

 only between four and five inches. No spring was ever 

 found ; but the shaft filled with mud, from the moisture 

 of the ground mixing with the earth displaced in boring, 

 which was peculiarly favorable for the experiments, as 

 the temperature at each depth may be considered to be 

 that of the particular stratum. In this case, where none 

 of the ordinary causes of disturbance could exist, and 

 where every precaution was employed by scientific and 

 experienced observers, the temperature was found to 

 increase regularly and uniformly with the depth at the 

 rate of about 1 of Fahrenheit for every 52 feet. Pro- 

 fessor Reich of Freyberg has found that the mean of a 

 great number of observations both in mines and wells is 

 1 of Fahrenheit for every 55 feet of depth, and from 

 M. Arago's observations in an Artesian well now boring 

 in Paris, the increase is 1 of Fahrenheit for every 45 

 feet. Though there can be no doubt as to the increase 

 of temperature in penetrating the crust of the earth, 

 there is still much uncertainty as to the law of increase, 

 which varies with the nature of the soil and other local 

 circumstances ; but on an average, it has been estimated 

 at the rate of 1 for eveiy 50 or 60 feet, which corre- 

 sponds with the observations of MM. Marcet and de la 

 Rive. In consequence of the rapid increase of internal 

 heat, thermal springs, or such as are independent of 

 volcanic action, rising from a great depth, must neces- 

 sarily be very rare and of a high temperature, and it is 

 actually found that none are so low as 68 of Fahren- 

 heit : that of Chaudes Aigues in Auvergne is about 

 136. In many places warm water from Artesian wells 

 will probably come into use for domestic purposes, and 

 it is even now employed in manufactories at Wurtem- 

 berg, in Alsace, and near Stutgardt. 



It is hardly to be expected that at present any infor- 

 mation with regard to the actual internal temperature 

 of the earth should be obtained from that of the ocean, 



