30 REMAP.KS OX TEMPERATURE OF THE EARTH IN" MIXES, ETC. 



elusion that so far as practical mining is concerned, the theory 

 has been too hastily formed and on data altogether insufficient for 

 its establishment. As it is a matter of immediate importance 

 in our northern mining fields, however, I have taken this 

 opportunity of drawing attention to it, for investors will not care 

 to invest if they have the fact or theory before their eyes that at 

 the depth of 1,000 feet or so the mines must per force of nature 

 come to an end ; not on account of the cost of working, or the 

 poor return from the mine, but because of the supposed 

 impossibility of working in the intense heat of the surrounding 

 atmosphere. 



I indulge the hope, therefore, that one of its effects will be 

 to stimulate other observers, particularly in mines where the 

 ventilation is sufficient to carry off the abnormal or ad\"entitious 

 heat for which the normal state of the earth is not responsible ; 

 and will conclude by an extract from Sir. W. W. Smyth (with 

 which I entirely agree) who says : — " In South Wales and 

 Lancashire in the coal measures, and in certain districts where 

 the surface is occiipied by the red sandstone of the trias, we 

 may have coal seams beloAv at 5,000, 8,000, or 10,000 feet deep ; 

 some of the authors quoted think that the limit of accessible 

 depth is 4,000 feet beyond which the increase of temperature 

 would prevent the possibility of working, but a considerable 

 experience of deep mines induces me to believe that the 

 difficulties of temperature may by due appliances be overcome 

 to a much greater depth.'" 



