as observed at a Depth of 500 Yards, at Monk- We at mouth . 447 



the spirited attempt of Mr. Pemberton to reach the coal-seams 

 which underlay the magnesian limestone of Durham, by a 

 shaft at Monk-Wearmouth which had then reached the ex- 

 traordinary depth of 250 fathoms. I mentioned to M. Arago, 

 while he was in Newcastle, my great desire to examine in this 

 pit, the question of subterranean temperature, before the or- 

 dinary processes of a deep colliery had complicated the inves- 

 tigation with unascertainable conditions; and was happy to 

 find that a view which I had formed, of relying very much 

 on trials made in subterranean small feeders of water, met 

 with his approval. 



3. Professor Whitley, of Durham, had also considered the 

 subject in another point of view, and on my return to New- 

 castle, I found my friend Mr. W. L. Wharton, of Dryburn, 

 engaged in arrangements for a course of experiments in the 

 pit, which, at the enormous depth of 264 fathoms, had passed 

 through a seam of coal 6 feet in thickness. Every facility 

 being kindly offered by the proprietors of the colliery, (Messrs. 

 Pemberton and Mr. Thompson,) I descended the pit for the 

 purpose of the experiments on Saturday the 15th of Novem- 

 ber, at 1 1 a.m., and remained nearly four hours underground, 

 with the following gentlemen, viz. Mr. W. L. Wharton, Pro- 

 fessor Whitley, Rev. Prof. Chevallier, Prof. Johnston, Mr. 

 G. C. Atkinson, and several others. 



Barometers and thermometers were taken by Mr. Wharton 

 and myself, and each of the other gentlemen was provided 

 with a thermometer. On a comparison of thermometers from 

 47° to 70°, it was found that Mr. Whitley's (by Adie) agreed 

 with one constructed by myself. By this standard, all the 

 observations are recorded, proper corrections being applied 

 to the other instruments. 



4. The pit is 12 feet in diameter, partitioned in the usual 



Seam of coal at 264 fathoms. 

 Bottom of Pit. 



manner, and tubbed in parts to stop the entrance of water, 



