58 



Prof. J. Prestwich. 



Locality. 



11. Brittany, Poullaouen 



12. 



Hueleoet 



13. Freiberg, Saxony 



14. Whitehaven. 



15. Workington . 



16. Percy Main. . 

 11. Killing worth. 

 18. Cornwall . . . 



19. 



20. 



Dolcoath 



Huel Vor 



II 



Place of observation. 



Lead and silver mine 



Lead and silver mine 



Alte Hoffnung Gottes . . 

 Silver mine 



Coal pit 



5> 



5> 



Various copper and tin 

 mines 



Copper and tin mine 



Tin 



III 



Height of 

 surface 

 above 



sea-level. 



Feet. 



34$ 



568 



1300 ? 



50—100 



100—500 



280 



* In Cornwall a mean surface temperature of 50°, 51°, 52°, or even 53° F. was 

 adopted in the early underground observations, and thermometric gradients were 

 calculated on those several different scales. The more recent observations of mean 

 annual temperature, which I have received from the Meteorological Office, give for 

 Penzance 51-8°, Truro 52°, Falmouth 51'4°, while Plymouth is 5T3°, and the high 

 ground of Dartmoor 45'8°. Taking the height of the mining districts to vary from 

 100 to 800 feet, we may take the mean annual temperature of those districts 

 " in block " at 51°. Mr. E. Were Fox placed thermometers 3 feet underground, 

 at a height of 300 feet above the sea-level, near Dolcoath Mine, which gave a mean 

 annual temperature of 49'94° F. ; at 300 feet near Grooland Mine, which gave 

 48 - 99°; and at 120 feet at Falmouth, where it recorded 50"67 o . His opinion was 



