A FEW WORDS ABOUT .COAL. 313 



spends precisely, in one case, to that of a capital of 

 120,000,000 sterling, increased each year by simple 

 interest at the rate of 3| per cent., while, in Mr. 

 Jevons's method of calculation, the increase is as that 

 of a capital of 120,000,000 sterling, increased by com- 

 pound interest at the rate of 3J per cent, per annum. 

 To give an idea of the actual difference as respects the 

 consumption at some distant epoch, let us take the 

 year 1950. Then, according to the former method of 

 viewing the matter, the consumption in that year will 

 be 373i millions of tons ; according to the latter, the 

 consumption would be no less than 1,446 millions ! 



Startling as this result may seem, the commissioners 

 found that in the last year of the five during which 

 their labours continued, the consumption corresponded 

 much more closely with the anticipations of Mr. Jevons 

 than with the theory of an arithmetical rate of increase. 

 And they remarked thereon that, though ' every hypo- 

 thesis must be speculative, it is certain that, if the 

 present rate of increase in the consumption of coal be 

 indefinitely continued, even in an approximate degree, 

 the progress towards the exhaustion of our coal will be 

 very rapid.' 



This will readily be believed when we mention that, 

 according to Mr. Jevons's method of calculation, 

 adopting 3'26 as the rate per cent, of increase, 

 150,000 millions of tons as the total available supply 

 of coal, and 120,000,000 as the present annual con- 

 sumption, our coals would not last us quite 127 years. 



I venture, however, to indicate reasons for believ- 



