318 THE BORDERLAND OF SCIENCE. 



of coal. Nor is it at all unlikely that before long 

 inventions will be so directed as to reduce, in a very 

 marked manner, the consumption of coal in certain 

 departments of trade and commerce. 



Now, if this view of the future is just, we can no 

 longer apply a percentage of increase after Mr. Jevons's 

 method, except for so moderate a number of years that 

 the monstrous annual consumption indicated for 1950 

 (for example) is no longer in question. For the next 

 ten, twenty, or even thirty years, it is not vitally im- 

 portant whether we take Mr. Jevons's method or Mr. 

 Hull's. There would, indeed, be a considerable differ- 

 ence in the annual consumption at the end of the ten, 

 twenty, or thirty years ; but still the main differ- 

 ence would be that a certain consumption would be 

 reached so many years sooner in one case than in the 

 other.* Thus, taking 120 millions of tons as the 

 present annual consumption, and 3*26 as the rate of 

 increase per cent, per annum, the annual consumption 

 ten years hence will be 159 millions of tons if the 

 actual increase remain constant, and 165 millions T1 of 

 tons if the percentage of increase remain constant ; at 

 the end of twenty years the numbers will be respec- 

 tively 185 millions and 227 millions ; at the end of 



* It will be very soon in our power to decide whether one or other 

 hypothesis be correct ; nor will it be long before it will be possible to 

 decide whether the hypothesis advocated by myself is not sounder 

 than either. I venture to predict that before the year 1890 the per- 

 centage of increase will be markedly below Mr. Jevons's estimate ; 

 and that before the year 1900 the actual increase will be below its 

 present value. 



