THE LIMITS OF OUR COAL SUPPLY. 205 



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 rocks. But in the conver- 

 sion of water at 60 into vapor at say 100, 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 

 enterely 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, prat 

 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 con- 

 cerned, 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 110 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 com- 

 pared to the red-hot radiant surfaces to which puddlers, 

 shinglers, glassmakers, etc., 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 vapor a sturdy midland or north-country- 

 man would work merrily enough at short hours and high 

 wages, even though the newly-exposed face of 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 steamship stoke-holes. 



The high temperature at 8000 or even 10,000 feet would 

 present a really serious difficulty during the first opening of 

 communications between the two pits. A spurt of brave 



