198 report— 1877. 



expected to be itself pretty near the temperature of the rocks through which 

 it is circulating." 



Ihe dryness of the mine, the absence of currents of air, and the great depth 

 render these observations extremely valuable for the purpose which the Com- 

 mittee have in view ; and their best thanks are due to Mr. Heckels and the 

 proprietors of the colliery for the trouble and expense which have been in- 

 curred in procuring them. Observations will shortly be taken in another 

 bore in the same colliery. 



During the past year the first observations have been received from India. 

 They were taken by Mr. H. B. Medlicott, M.A., of the Geological Survey, in 

 holes made in search of coal, and have been published by him in the ' llecords 

 of the Geological Survey of India,' vol. x. pt. i. The instrument employed was 

 a protected Negrotti thermometer, sent by the Secretary of this Committee to 

 Dr. Oldham, the Director of the Survey. A Casella-Miller thermometer was 

 used to check the observations, but was found much less sensitive and steady, 

 and its readings, though placed on record, are therefore left out of account 

 by Mr. Medlicott in his reductions. 



The observations were taken in three bores, at places named Khappa, 

 Manegaon, and Moran ; but the observations at Moran were made only fcur 

 hours after the boring tool had been at work ; and the Khappa bore exhibited 

 a strong bubbling, besides other marks of convection. The results obtained 

 at these two bores must therefore be discarded : but in the Manegaon bore 

 every thing was favourable for satisfactory observation. "It was closed on 

 the 24th of April, 1875, so that it had been at rest for 20 months. There is 

 only one guide-pipe, ten feet long, at the top of tho bore, there never having 

 been any pressure of water in the hole. The position is low, and the water 

 had always stood at or near the mouth of the tube. There was no difficulty 

 in removing the plug. The very equable series of temperatures is the natu- 

 ral result of these conditions. The observations were taken in the evening 

 of the 5th and morning of the 6th of December. At 5 p.m. the air temperature 

 was 72° ; at 8 r.M., 5!,°; at 8 a.m., 65°; at 11 a.m., 8-1°. Tho slight decrease 

 of temperature in the top readings is a good proof of the perfectly tranquil 

 conditions of observation. It is no doubt due to the excess of summer In at 

 not yet abstracted ; and it is apparent that that influence reaches to a consi- 

 derable d( pth, quite to 60 feet." The following arc the observations : — 



Depth in Temperature 



feet. Fahr. 



10 81-15 



20 81-1 



40 81-0 



60 81-0 



80 81-3 



100 81-8 



150 82-7 



200 83-3 



250 84-0 



300 84-65 



310 84-70 



The observation at 310 feet was in mud, the hole, which had originally a 

 depth of 420 feet, having silted up to such an extent that 310 feet was the 

 lowest depth attainable. The increase from 60 feet downwards is remarkably 





