460 On the Rate of Increase of Underground Temperatures. 



ble with the rapidity of winding up ; also in part to the circum- 

 stance that the wire is warmer when it has just left the water 

 i it is about to be let down. Some portion of the 

 irregularity observed may be due to variations of temperature 

 in that part of the well (210 feet) which contains air. The 

 observations, taken as a whole, show that any variations of tem- 

 perature which occur in this well nt the depth of 1,000 feet, 

 are so small as to be comparable with the almost inevitable 

 errors of observation. The observations will be continued at 

 intervals of six months, with adding a! precautions, and with 

 an excessively slow (specially constructed) non-registering ther- 

 mometer, in addition to the maximum thermometer hitherto 

 employed. 



Through the kindness of the eminent geologist, M. Delesse, 

 of the Ecole Normale at Paris, observations have been obtained 

 from the coal mines of Anzin, in the north of France. They 

 were taken under the direction of M. Marsilly, chief engineer 

 of these mines. Maximum thermometers of the protected 

 N. •■_•!■ :ti pattern, were inserted in holes bored hori;. 

 the depth of *6 or '7 of a meter in the sides of sb 

 were in process of sinking, and in which there was but little 

 ;i of air. A quarter of an hour was allowed to elapse 

 in each case, after the boring of the hole, before the thermo- 

 meter was inserted, and the hole plugged. Four different 

 shafts were tried. Those designated as Nos. I, II, III, were 

 in the mine Chabaud La Tour ; and No. IV was in the mine 

 Eenard. 



In Shaft I, observations were taken at eight differei 

 commencing with the temperature 56J° F. at the depth of 38*5 

 meters, and ending with 67|° F. at 200'5 meters. 



In Shaft II there were observations at four depths, com- 

 mencing with 55° at 87"8 m., and ending with 63£° at 185 m. 



In Shaft III there were observations at three depths, com- 

 mencing with 56° at 87"8 m., and ending with 62£° at 144 m. 



These three shafts, all belonging to the same mine, were very 

 wet, and the temperature of the air in them was 11° or 12° C. 

 (52° or 54° F.). 



In Shaft IV, which was very dry and had an air temperature 

 of about 15° C. (59° F.), observations were taken at six depths, 

 commencing with 70f° F. at 21-2 m., and ending with 84° F. at 

 134-8 m. 



The mean rates of increase deduced from these observations 



In Shaft I, 1° F. in 14-4 m., or in 47"2 feet. 



