210 REPORT— 1876. 



The "• depth indicated " is shown by a measuring wheel or pviUey, over- 

 which the wire runs by which the thermometer is raised and lowered, as 

 described, with a diagram, in the Eeport for 186t). The above Table shows 

 that there is always some stretching, real or apparent, in the interval be- 

 tween lowering the thermometer and raising it again. Hecent observations, 

 by means of a fixed mai'k on the wire, have shown that the change is not, 

 in the main, a permanent elongation, but an alternation of length. It is 

 probably due in part to the greater tension which the wire is iinder in rais- 

 ing than in lowering, a circumstance wliich will cause a temporary differ- 

 ence of length variable with the rapidity of winding up ; also in part to the 

 circumstance that the wire is warmer when it has juet left the water than 

 when it is about to be let down. Home 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 temperature which occur in this well at the depth of 1000 feet 

 are so small as to be comparable with the almost inevitable errors of ob- 

 servation. The observations will be continued at intervals of six months, 

 with additional precautions, and with an excessively slow (specially con- 

 structed) non-registering thermometer, in addition to the maximum ther- 

 mometer hitherto employed. 



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

 j^ormale at Taris, observations have been obtained from the coal-mines of 

 Anziu, in the north of Prance. They were taken under the direction of 

 M. Marsilly, chief engineer of these mines. Maximum thermometers of 

 the protected Xegretti pattern were inserted in holes bored horizontally to 

 the depth of -G or -7 of a metre in the sides of shafts which were in pro- 

 cess of sinking, and in which there was but little circulation of air. A 

 quarter of an hour was allowed to elapse in each case, after the boring of 

 the hole, before the thermometer was inserted and the hole plugged. Four 

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

 the mine C^haband La Tour, and No. TV. was in the mine Eenard. 



In shaft I. observations were taken at eight different depths, commencing 

 with the temperatiu'c 56|° F. at a depth of 3S-5 metres, and ending with 

 (171° F. at 200-5 metres. 



In shaft II. there were observations at four depths, commencing with 

 55° at 87-3 m., and ending with G3j° at 185 m. 



In shaft III. there were observations at three depths, commencing with 

 5G° 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 themVas 11° or 12° C. (52° or 54° F.). 



In shaft lY., which was very dry and had an air temperature of about 

 15° C. (59° F.), observations were taken at six depths, commencing with 

 70|° F. at 21-2 m., and ending with 84° F. at 134-8 m. 



The mean rates of increase deduced from these observations are: — 



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

 II., „ 11-5 m., „ 37-7 „ 

 „ III., „ 8-G5m, „ 28-4 „ 



IV., „ 8-57 m., „ 28-1 „ 



The observer mentions that in shaft II. there was, at a depth of 90 m., a 

 seam of coal in which heat was generated by oxidation; but no such 

 remark is made with respect to any of the other shafts, although it is 

 obvious that some disturbing cause has rendered the temperature in shaft 

 IV. abnormally high. Possibly the heat generated in boring the holes for 



