244 Mr Hen wood on the temperature of Mines. 



lion ?" Mr Fox is disposed to think that the isothermal Hnes 

 within the earth may in some measure coincide with the form 

 of its surface. 



Another point to wliich attention has been directed is the re- 

 lative temperatures of the metalliferous veins, and the adjacent 

 strata at some distance from them. Of these observations the 

 followintr table contains the substance. 



Mine. 



Depth. 



Distance from the 

 veins at which obser- 

 vations were made 

 in the strata 



Vein. 



Little Bounds, 

 Huel Neptune, 

 Ting Tang, 



30 fathoms. 



Huel Squire, 

 Chacewater, 

 Treskerby, 

 Dolcoath, 

 United Mines, 140 

 160 



52 Unoticed. 



49 



80 



90 



110 



no 



110 

 1^.0 

 130 



Temperature.* 

 Strata. 



54iW 



j 54° w? \ 

 \56w J 



Observers. 



Forbes. 



unnoticed. 



60 fathoms. 



9 — 



8 



64 e 

 68 e 



S2e 



72 a 

 6Se 

 67 w 



75 e 



} 



64 e Fox. 



69 fl 

 79 a 



66 a 

 62 e 



67 e 

 69 e 



An obvious inference is, that the temperature of veins is 

 generally rather superior to that of the contiguous strata. The 

 subject of the temperature of the interior of the earth has led 

 to many ingenious theories of its structure and relations. 

 Among these, that which supposes the central regions to exist 

 in a liquid state, subject to the action of a very elevated heat, 

 seems to be gaining ground. Were the high temperatures ob- 

 served due to such agency, it would naturally be expected 

 that the closer the texture and the better the conducting power 

 of any given substance, the greater would be the elevation of 

 temperature observed therein. But casteris paribus, our granite 

 and porphyriiic rocks, although far surpassing clay-slate and 

 metalliferous veins in both these circumstances, are generally 

 found at a lower temperature than any other of our strata or 

 formations. Mr Fox remarks, that the high temperature " may 



' * Of the letters, a signifies that the experiment was in the air, e the 

 earth, and w the water. 



