404. 



THE GEOLOGIST. 



lode in this deep level, at its eastern extremity, was 90° 5^ ; the conti^ous 

 granite, 91° 5' ; the air, 91* 5' ; a small spring of water flowing from the lode, 

 93" ry. ' In 1837, the deepest level in this mine was 262 fathoms, or 1,572 feet, 

 beneath the surface, and the terapeniture of the rock was then 82° 5\ 



Dolcoath (in the parish of Camborne) is a very productive mine of copper and 

 tin, and now yields much of the latter in its deepest part, the containing rock 

 being granite, with kiilas near the surface. The deepest level on the north lode 

 was 272 fathoms below the surface, and extended only about four fathoms on 

 each side of the engine-shaft ; the rock at its eastern end was 73'^ 5' ; the air, 

 71" 7'; and the water, 73°. At the western end, it was 73° on one side of the 

 level, and 73° o' on the other ; the air, 73° ; and the water, the quantity of which 

 was very small, 72° 7\ At about three fathoms further south, and at the same 

 depth, another lode was worked, the level extending to about fourteen fathoms 

 to the westward of the engine-shaft. The granite was found to be at 79° 6' ; and 

 the water, which was much more abundant than in the other level, 79° d' ; while 

 the air was at 78°. 



In 1821-22, the deepest level in Dolcoath was 230 fathoms from the surface, 

 and Mr. Fox then had an accurate thermometer, 4 feet long, kept in it for more 

 than a year, with the bulb sunk 3 feet in the lode ; and it varied from 75° and 

 75° 5' to 76° 5' and 77° ; an occasional influx of water having caused a temporary 

 rise of the mercury to the extent of a degree or more. 



The water near the bottom of the engine-shaft in 1822 was at 82° at 239 

 fathoms below the surface; and last year (1857) it was 82° 5', at 278 fathoms 

 deep. 



The deepest level of the Levant copper and tin mine, in St. Just parish, is 255 

 fathoms below the surface of the ground, and nearly 230 fathoms beneath the 

 sea-level, having been extended horizontally under it through kiilas. The tempe- 

 rature of the rock near the end of the level was 84° 7' on one side and 85° 5' on 

 the other ; the water, 85° 5' ; the air, 85°. In 1853, the temperature of the 

 reck in this level, when it was not extended so far westward under the sea, was 

 reported to be 87°, and the granite rock at the same level, eastward of the shaft, 

 74°. 



Botallack copper and tin mine is in the same parish. The western levels extend 

 through kiilas far under the Atlantic, one of them more than half-a-mile from the 

 shore. The deepest level was 188 fathoms from the ground and 180 under the sea- 

 level ; the rock near the end being 79° on one side and 79° 5' on the other ; the 

 air, 81°. 



These results exhibit great difi"erences in the rates of increase in the temperature 

 in different mines, and also in different parts of the same mine, as will be better 

 seen in the following table, prepared by Mr. Fox, in which the experiments made 

 in the deepest levels are arranged in order of their respective depths, and which 

 exhibits the ratios in feet, in descending from the surface in which the tempera- 

 ture was augmented 1° Fahr. from 50°, the mean temperature of the climate ; — 



Mines. 



Par Consols (tin part) ... 



]?otallack, C. and T 



Par Consols (copper part) 



Dolcoath, C. and T 



Levant, C. and T 



Levant, C. and T 



Levant, C. and T 



Tvesavean, C .. 



Dolcoath, C. and T 



Dolcoath, another lode... 

 Tresavean, C 



in f( ' ■ 



m 









Increase of 





a> 



Temperatures. 



1° in 



Eocks 



ft 









descending. 





768 



1837 



74° 



-50 = 



24° 



32 feet. 



Kiilas. 



1128 



1837 



79 



-50 = 



29 



39 „ 



Kiilas. 



1248 



1837 



84 



-50 = 



34 



36-7 „ 



KiUas. 



1380 



1822 75-5 



-50 = 



25-5 



54 „ 



Granite. 



153C 



185374 



-50 = 



24 



63-7 „ 



Granite. 



1530 



1853 87 



-50 = 



37 



41-3 „ 



Kiilas. 



153C 



1857 



85 



-50 = 



35 



43-7 „ 



Kiilas. 



1572 



1837 82-5 



-50 = 



32-5 



48-4 „ 



Granite. 



lG:i2 



1857 



73 



-50 = 



23 



71 „ 



Granite. 



1632 



1857 



79-5 



-50 = 



29-5 



55-3 „ 



Granite. 



2112 



1858 90-5 



1 



-50 = 



40-5 



52-1 



Granite. 



