1,94 SCIENCE IN SHORT CHAPTERS. 



millions of tons, which, at present rate of consumption, 

 would last about 1200 years. But the rate of consumption 

 is annually increasing, not merely on account of increasing 

 population, but also from the fact that mechanical inven- 

 tions are perpetually superseding hand labor, and the 

 source of power in such cases. is usually derived from coal. 

 This consideration induced Professor Jevons, in 1865, to 

 estimate that between 1861 and 1871 the consumption 

 would increase from 83,500,000 tons to 118,000,000 tons. 

 Mr. Hunt's official return for 1871 shows that this estimate 

 was a close approximation to the truth, the actual total for 

 1871 having been. 117,352,028 tons. At this rate of an 

 arithmetical increase of three and a half tons per annum, 

 139,000 millions of tons would last but 250 years. Mr. 

 Hull, taking the actual increase at three millions of tons 

 per annum, extends it to 276 years. Hitherto the annual 

 increase has followed a geometrical rather than arithmeti- 

 cal progress, and those who anticipate a continuance of 

 this allow us a much shorter lease of our coal treasures. 

 Mr. Price Williams maintains that the increase will pro- 

 ceed in a diminishing ratio like that of the increase of pop- 

 ulation; and upon this basis he has calculated that the 

 annual consumption will amount to 274 millions of tons a 

 hundred years hence, and the whole available stock of coal 

 will last about 360 years. 



The latest returns show, for 1872, an output of 123,546,- 

 758 tons, which, compared with 1871, gives a rate of in- 

 crease of more than double the estimate of Mr. Hull, and 

 indicate that prices have not.yet risen sufficiently to check 

 the geometrical rate of increase.* Mr Hull very justly 

 points out the omission in those estimates which, do not 

 "take into account the diminishing ratio at which coal 

 must be consumed when it becomes scarcer and more ex- 

 pensive;" but, on the other hand, he omits the opposite in- 

 fluence of increasing prices on production, which has been 

 strikingly illustrated bjj the extraordinary number of new 



*From 1870 to 1880 the amount has risen from 110,431,192 to 146,- 

 818,622 tons per annum, an average increase of 3,638,743 tons per 



aunum. 



