AI^yiVERSAllY ADDRESS OF THE PRESIDENT. IxXXV 



South Hoo Lead-mine, near Callington. 



Surface, 30th October 1863, at 9.30 a.m 50° 



215 fathoms level, in south end of lode ' 79 



226 do. out of the air-current 83 



237 do. behind a pile of stuff, in end 92 



250 do. out of air-current 88*5 



The above are, in all the deeper levels, maximum temperatures, 

 increased beyond the normal by want of adequate ventilation. 



Fowey Consols Copper-mine, East Cornwall. 



Surface at 11 a.m., October 1866 61° 



140 fathoms level, on footway lode, far from air-current 86 



240 fathoms level, water in cross course 96 



270 do. end near Bothall's shaft 88 



280* do. do 89 



In tbe latter inspection I was accompanied by Mr. Kendall, M.P., 

 F.G.S. ; and we found that, whilst the remainder of the workings were 

 considerably cooled down in the series of years since they were first 

 laid open, the above jjoints showed exceptionally high temperatures, 

 and the water in the cross course at the 240 fathoms level was so 

 much hotter than it ought, from mere depth, to be, that it might be 

 regarded as a thermal spring. 



Lastly, a remarkable instance is offered by the great tin-mine 

 "Wheal Yor, near Helston, where, leaving (30th September 1858) a 

 midday temperature of 67° at surface, I descended to the bottom 

 immediately after the water (which had occupied it for many years) 

 had been extracted, and found, at 284 fathoms depth from adit, or 311 

 fathoms from surface, the air and the water issuing from the rock 

 both at 80° Fahr. The ruinous expense which beset the resumption 

 of this old work occasioned its very soon being again closed ; but it 

 was curious and somewhat unexpected to find the temperature no 

 higher at the 284 fathoms level than it was recorded at 240 fathoms 

 twenty years before by Mr. W. J. Henwood ; and the explanation 

 is probably to be found in the sea of surface-water which had for a 

 long time before my visit occupied the excavations as well as the 

 joints and fissures of the rock around them, and was still pouring 

 down on all sides of the great open stopes of the bottom of the mine. 

 Observations made a few months afterwards by Capt. Francis, and 

 published by Mr. Henwood, state that different parts of the same 

 deep level then showed temperatures of from 82° to 90°. It was quite 

 evident that, as usual, what was at one time the bottom of the mine, 

 had become cooler when, after a series of years, other workings had 

 been opened beneath it ; but, as Mr. Henwood insists, the same 

 locality still maintained a higher temperature than the mean of the 

 shallower parts of the mine. And I am inclined to think that the 

 actual bottom at the time of my visit may have suffered refrigeration 

 by the rock parting with its heat to the currents of cold water 



* To give the absolute depth from surface at the shaft, 40 fathoms may be 

 added to the nominal depth of each level, the adit being at that depth from the 

 mouth of the shaft. 



