26 RKJIARKS ON TEMPERATURE OF THE EARTH IN MINES. 



mine is nearly stationary ; that by being breathed by a number 

 of men it loses its vital properties ; that it is poisoned to some 

 extent by noisome exhalations ; that it becomes charged with 

 the fumes of explosives ; and that there are occasionally out- 

 bursts of hydrogen gas where saline water falls on blende ore. 

 Added to these considerations, there is also the natural increase 

 of the temperature of the earth downwards towards its centre." 

 It must be borne in mind that the writer here speaks of metal- 

 liferous mines, and it is passing strange that, with a stationary 

 atmosphere and all these sources of heat, it should never have 

 occurred to him that these are really the chief, if not the only 

 cause of the increase of temperature of the earth downAvards 

 towards its centre. 



Davies continues, " concerning this last remark, I may here 

 notice incidentally, that from observations made by jMr. Henwood 

 in Cornwall, Professor Phillips in the North of England, Mr. 

 Bryham in Lancashire, and Professor Reick in Saxony, as well 

 as from the results obtained by other observers, the temperature 

 ■of the earth increases downward at a rate varying from 1 degree 

 Fahrenheit for every 45 feet in depth to I degree Fahrenheit for 

 every 7G feet in depth. It may be taken as the average result 

 that the rate of the increase of heat is 1 degree Fahrenheit for 

 every 65 feet in depth." 



I have already quoted largely from Henwood ; the obser- 

 vations of Professor Phillips and Mr. Bryham were chiefly, if 

 not entirely, taken in the coal measures where the adventitious 

 sources of heat are exceptionally numerous and great, and do 

 not much concern us in the present question, and those of Pro" 

 fessor Reick are not at hand, but would probably be affected by 

 the same adventitious causes. 



In confirmation of the views put forward touching the 

 cause of heat " The Useful Metals and their Alloys " may be 

 quoted, which states that " the temperature of the air in Cornish 

 mines, at great depths, has been generally found to exceed, by 

 some degrees, the temperature of the lode. This can only be 

 attributable to the heat given oft' by the men and the lights, and 

 is a proof of the stagnant state of the air;" again, " the loss in 

 amount of work performed at high temperatures offers a large 



