82 LIGHT SCIENCE FOR LEISURE HOURS. 



hand, if we add eight years' increase to the consumption 

 of 1863 (88,292,515 tons), we obtain 107,519,907 tons. 1 

 It will be seen that there is an important difference 

 between the consumption for 1 871, as estimated accord- 

 ing to Mr. Jevons's view, and according to the average 

 rate of increase in the nine preceding years. As the 

 matter stood in 1865, the great question concerning 

 the consumption of the year 1871 would have been, 

 whether it would be nearer 118 millions, the estimate 

 of Mr. Jevons ; or to 107^ millions, the estimate, accord- 

 ing to the annual rate of increase ; or, lastly, to a num- 

 ber of tons, not much, if at all, exceeding 100 millions ? 

 The answer of the Commissioners comes in no doubt- 

 ful terms. Judging from the consumption during the 

 four years ending in 1870, the estimated consumption 

 for the year 1872 is no less than 115 millions, an 

 amount approaching Mr. Jevons's estimate much more 

 nearly than could be desired. Indeed, if we consider 

 the imperfect nature of the statistics on which he 

 founded his calculations, the agreement between his 

 estimate and the observed result must be regarded as 

 surprisingly close. Eemembering the conclusion to 

 which Mr. Jevons came with respect to the period for 

 which our coal stores would last, and noticing the close 

 agreement thus far between his anticipations and the 

 result, we can well understand the warning tone of 

 the report issued by the Commissioners. < Every hypo- 



1 The year 1863 was the last whose statistics were available for 

 Mr. Jevons's purpose ; and estimating from either 1860 or 1862 would 

 give a result smaller than either of the above. Indeed, the con- 

 sumption was less in 1862 than in 1861. 



