ON UNDERGROUND TEMPERATURE. 19 



from a level at the depth of 398 feet below ground, and the surface of the 

 water in it is 399 feet down the shaft, or 797 feet below the surface of the 

 ground. There are pumps in the shaft, but they had been stationary for more 

 than 24 hours before the observations were made. Immediately after the 

 observations they were started, and when they had been working for some 

 time the temperature of the water lifted was found to be 65°-2. They draw 

 their water at a depth of 957 feet below the surface of the ground. 

 The following were the observations : — 



Depth under Depth in Temperature, 



ground. water. Fahr 

 ft. ft. 



807 10 65-n 



807 10 64-9 f 



857 60 65-41 



857 60 65-7 f 



807 10 65-4 



The thermometer could not be lowered beyond 857 feet without risk of 

 losing it, by getting fast in the wooden framework with which the pumps 

 were secured. Mr. Burns thinks that some of the temperatures here re- 

 corded are too low, from the index being shaken down by reason of the im- 

 pediments presented by the upper portions of the framework. The surface 

 of the ground over this shaft is about 300 feet higher than over Gin-Hill 

 shaft. If we allow 1° for this increase of height, and call the temperature of 

 the surface of the ground 44°-3, as against 45°-3 at Gin Hill, we have, by 

 comparison with the observed temperature 65°-7 at the depth of 857 feet, 

 an increase of 21°-4 in 857 feet, or 1° in 40 feet. 



On the 6th July Mr. Eidley took observations in another sump or under- 

 ground shaft at Slitt mine, Weardale. This shaft is sunk from the lowest 

 level in the working, and had been standing full of water during the five 

 months which had elapsed since it was sunk. The only source of disturbance 

 was a little water running along the level across the top of the shaft, so as 

 to enter the shaft (so to speak) on one side and leave it on the other. This 

 may affect the temperature at 3 feet, but could scarcely affect the tempera- 

 ture at 53 feet, which may be regarded as veiy reliable. 



The following are the observations ; — 



Depth under Depth in Temperature, 



ground. water. Fahr. 



ft. ft. 



610 3 64-51 



610 3 64-5 f 



660 53 65-li 



660 53 64-9/ 



Mr. Burns says " the surface-temperature at Slitt mine will be nearly the 

 same as that at Gin-Hill shaft, judging from their relative elevations, 

 aspects, and [exposure to the winds." Assuming it then to be 45°-3, and 

 reckoning the temperature at 660 feet as 65°, we have an increase down- 

 wards of 19°-7 in 660 feet, or 1° in 33-5 feet. The only datum that seems 

 doubtful here is the surface-temperature. If, instead of 45°'3, it be assumed 



f 44°-3 ) f ^1 Q 1 



as j 4go.3 y , it gives an increase of 1° in i g^'^ I feet. 



Mr. Eidley has also taken observations in Breckon-Hill shaft, which is 

 near the river Allen, about 1^ mile from Gin-HiU shaft, and at an elevation 



c2 



