On Underground Temperatures. 



37 



Depth. Temp. 



160 feet 47-5° 



200 „ .... 47 



250 „ .... 47-7 



300 „ .... 477 



One of the pits at Allenheads (No. 130) which was nearly full of 

 water gave similar results. 



Depth. Temp. 



50 feet 47-2° 



100 „ .... 46-8 



200 „ .... 46-6 



350 „ .... 46-9 



While in another shaft at Ashburton 620 feet deep, and with water 

 standing to within 50 feet from the surface, the temperature at all 

 depths was 53°, except at one point, where it rose to 53*4° and 53'2°. 



Even in the deep and narrow bore- hole at Sperenberg, it was shown 

 that the first experiments with thermometers protected against 

 pressure, but not against convection currents, gave wrong results, for 

 in the first instance at a depth of 100 feet, the temperature was 

 found to be 11° R., and at 3390 feet, 34*1° R. Afterwards, when 

 plugs were inserted to stop the currents, the temperatures at the 

 same respective depths had altered to 9° R. and 36*16° R., showing 

 therefore that the first readings were too high by 2° Reaumur near 

 the top of the bore, and too low by 2*05° Reaumur at the bottom. 

 Another experiment in the same well later showed that the difference 

 at the bottom, between plugging and no plugging, was as much as 

 6f° Fahr* 



Another narrow bore-hole, showing clearly the action of convec- 

 tion currents, was that sunk to a depth of 2000 feet, at Swiuderby, 

 Lincoln (No. 143). f The hole had remained undisturbed for nearly 

 three weeks, and the water stood within a few feet of the top. 



Depth. Temp. 



100 feet' . .. 68° F. 



300 „ .... 68-75 



500 „ .... 6875 



600 „ .... 69 



900 „ 69 



1200 „ .... 69-5 



2000 „ .... 79 



Taking the mean annual, temperature of S winder by at 48°, this 



* Brit. Assoc. Report for 1876, p. 205, and 1882, p. 3. The differences were 

 even considered to be under-estimated. 



f Brit. Assoc. Reports for 1875 and 1876. Part only of these are in Table I. 



