356 Limits of our Coal Supply. [July, 



most porous of the strata. Streams of cold water could 

 thus be poured down the sides of the shaft, which, on 

 reaching the bottom would flow by a downhill road into the 

 workings. The stream of air rushing by the same route 

 and becoming heated in its course would powerfully assist 

 the evaporation of the water. The deeper and hotter the 

 pit, the more powerful would be these cooling agencies. 



As the specific heat of water is about five times that of 

 the coal-measure rocks, or the coal itself, every degree of 

 heat communicated to each pound of water would abstract 

 one degree from five pounds of rock. But in the conversion 

 of water at 6o° into vapour at say ioo°, the amount of heat 

 absorbed is equivalent to that required to raise the same 

 weight of water about 1000 , and thus the effective cooling 

 power on the rock would be equivalent to 5000 . 



The workings once opened (I assume as a matter of course 

 that by this time pillar-and-stall working will be entirely 

 abandoned for long-wall or something better), there would 

 be no difficulty in thus pouring streams of water and 

 torrents of air through the workings during the night, or at 

 any suitable time preparatory to the operations of the 

 miner, who long before the era of such deep workings will 

 be merely the director of coal cutting and loading 

 machinery. 



Given a sufficiently high price for coal at the pit's mouth 

 to pay wages and supply the necessary fixed capital, I see 

 no insuperable difficulty, so far as mere temperature is 

 concerned, in working coal at double the depth of the Royal 

 Commissioners' limit of possibility. At such a depth of 

 8000 feet the theoretical rock-temperature is 183 . 



By the means above indicated, I have no doubt that this 

 could be reduced to an air temperature below no , — that 

 at which Mr. Tyndall's shampooers ordinarily work. Of 

 course the newly-exposed face of the coal would have 

 its initial temperature of 183 ; but this is a trivial 

 heat compared to the red-hot radiant surfaces to which 

 puddlers, shinglers, glassmakers, &c, are commonly exposed. 

 Divested of the incumbrance of clothing, with the whole 

 surface of the skin continuously fanned by a powerful 

 stream of air — which, during working hours need be but 

 partly saturated with vapour — a sturdy midland or north- 

 countryman would work merrily enough at short hours and 

 high wages, even though the newly-exposed face of the 

 coal reached 212 ; for we must remember that this new 

 coal-face would only correspond to the incomparably hotter 

 furnace-doors and fires of the steam-ship stoke holes. 



