BRITAIN'S COAL CELLARS. 77 



increase of coal consumption between 1854 and 1863, 

 which is 2,403,424 tons, but the average rate per cent, 

 of increase, which is found by computation to be 3-26 

 per cent.' That is to say, for every hundred tons of 

 coal consumed in one year, 103 tons, or thereabouts, 

 would be consumed in the next taking one year 

 with another. Without entering into technicalities, or 

 niceties of calculation, it is easy to show the difference 

 between this view of the matter and a view founded 

 only on the average increase during so many years. 

 Consider 10,000 tons of coal sold in one year, then Mr. 

 Stanley Jevons points out that instead of that amount, 

 10,326 would be sold in the next ; and so far we may 

 suppose that the other view would agree with his. But 

 in the next, or third year (always remembering, how- 

 ever, that we must take one year with another), the 

 increase of 326 tons would not be merely doubled, 

 according to Mr. Stanley Jevons ; that is, the con- 

 sumption would not be only 10,652 tons: the 10,000 

 of the second year would be replaced by 10,326 tons 

 in the third year, and the remaining 326 would be 

 increased by 3 tons for each hundred, or by rather 

 more than 10^ tons ; so that in all there would be 

 10,662 tons, instead of 10,652. Now the difference 

 in this third year seems small, though when it is ap- 

 plied to about nine thousand times 10,000 tons it is by 

 no means small, amounting in fact to 95,000 tons; but 

 when the principle is extended to sequent years its 

 effects assume paramount importance. The small 

 increase is as the small increase of a farthing for the 



