} 



20 REPORT 1871. 



not much above the bottom of the valley, but 1174 feet above sea-level. It 

 was sunk some years ago, and has since stood nearly fuU of water. At the 

 time of the observations the surface of the water was 24 feet down the 

 shaft. The following are the observations taken in this shaft on June 

 13th :— 



Depth under Depth in Temperature, 



ground. water. Fahr. 



ft. ft. 



50 26 47-2 1 



50 26 47-2 1 



100 76 46-9" 



100 76 46-8 



150 126 46-8) 



150 126 46-7 J 



200 176 46-6 



250 226 46-8 



300 276 46-8 



350 326 46-9 



These observations were taken early in the morning, when the air and 

 springs were so cold as to allow the maximum thermometer to be cooled below 

 the temperature of the shaft. In order to test more thoroughly the apparent 

 uniformity of temperature from 100 feet down to 350 feet, Mr. Ridley took 

 a second series of observations, extending from the 22nd to the 27th June. 

 In these observations the thermometer was lowered in a tin case fiUed with 

 water colder than that of the shaft. The thermometer was supported within 

 the case in a vertical position by a wooden frame, and prevented from shak- 

 ing about. It was allowed to remain at each depth several hours, was then 

 lifted, and read with all possible care. The following are the observations 

 thus obtained : — 



Here the temperature is even more uniform than in the first series. As 

 to the causes of this uniformity, Mr. Burns remarks that the shaft is not 

 connected with any working, but is cut through solid strata. It is a 

 few yards to the east of the Allen, while, in the bed of that stream, and 

 making a great spread on the west side of the valley, is a bed of hmestone 

 nearly 70 feet thick, and dipping at an angle of about 10^ to the east. The 

 top of this limestone was cut in the shaft about 40 feet down, which occa- 

 sioned a great influx of ivater into the shaft, and drained a strong spring on 

 the other side of the river. 



It will be observed that the chief difference between the two sets of ob- 

 servations is just at the place where this limestone was cut. The second set 

 were taken after and during much rain, and the first set after a week of very 

 little rain. It appears probable that the difference of temperature at this 



