Mr Hen wood on the temperature of Mines. 



241 



That the veins are much more pervious to the passage of 

 water than the contiguous strata is a notorious fact ; and I 

 have before alluded to the greater extent of the superior than 

 of the inferior galleries. It therefore appears that the great- 

 er portion of water coming from above is probably intercepted 

 by the superior galleries, and passing through them to the 

 shafts, if of a relatively low temperature, descends. It may 

 be presumed that the water in the lower levels, being compa- 

 ratively stationary, exerts but little influence on that in the 

 shafts ; of which, however, it appears that we might expect to 

 find the temperature invariable at all depths. But we must 

 not forget that the mean temperature of wells, and at the sur- 

 face in stopped mines, is somewhat more than five degrees 

 above the mean of the climate ; and that in some mines, in the 

 lower levels of which operations have been suspended, and ac- 

 cumulations of water permitted, the temperature is very far 

 above 49.°86, as reference to the preceding table affords ample 

 evidence. On this part of the question Mr Fox remarks, " the 

 * The water at 10, 20, 40, and 60, fathoms deep was also at 54.° 



VOL. X. NO. II. APRIL 1829- Q 



