BRITAIN'S COAL CELLARS. 83 



thesis,' they say, * must be speculative, but it is certain 

 that if the present rate of increase in the consumption 

 of coal be indefinitely continued, even in an approxi- 

 mate degree, the progress towards the exhaustion of 

 our coal will be very rapid.' Let it be remembered 

 that the Commission was issued at the instance of those 

 who took the more sanguine view, and that it included 

 within its ranks such eminent authorities as Sir William 

 Armstrong, Sir Robert Murchison, Professor Eamsay, 

 Mr. John Hunt, and others of like experience in the 

 subject under inquiry. 



If, in the next place, we compare Mr. Jevons's esti- 

 mate of the quantity of coal available for use with the 

 result obtained by the Commissioners, we find little to 

 restore our confidence in the extent of time during 

 which our coal stores may be expected to last. We have 

 seen that 200,000 millions of tons had been supposed 

 to be available ; but the Commissioners find that 4 we 

 now have an aggregate of 146,480 millions of tons, which 

 may be reasonably expected to be available for use.' 

 Again, it had been supposed that our coal mines could 

 be worked to a depth of 4,000 feet, or to an even greater 

 depth. ' The difficulties in the way of deep mining,' 

 wrote Mr. Lemoran in 1866, ' are mere questions of cost. 

 It is important to notice that the assumption of 4,000 

 feet as the greatest depth to which coal can be worked, 

 on account of the increase of temperature, is purely 

 voluntary. The increase has been calculated at a rate 

 for which there is no authority ; and while we are saying 

 our coal-beds cannot be worked below 4,000 feet, a 



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