vii 



geometry. Those combinations possess an interest for the mathema- 

 tician apart altogether from their logical significance. (" Manchester 

 Proceedings," 1877, vol. xvi, pp. 89, 113.) 



In 1867 Professor Jevons married Harriet Ann, daughter of the 

 late John Edward Taylor, the originator, proprietor, and editor of the 

 <l Manchester Guardian." Three children were the fruit of the union, 

 a son born in 1875, and two daughters, one born in 1877, the other in 

 1880. His domestic happiness, and the composure of mind resulting 

 from it, facilitated largely the execution of his intellectual work. He 

 confessed to it himself with his usual manly simplicity, and, as one of 

 his friends says, "it was as if his very powers as an observer had 

 derived a fresh and lasting impulse from the new associations which 

 had become part of his life." 



The question of the extent and the resources of the British coal- 

 fields was brought under public notice by the debates in Parliament 

 on the Commercial Treaty with France in 1859-60. Attention was 

 called to the importance of effecting a reduction in the National Debt, 

 while coal and iron, the main sources of British wealth, were 

 abundant. Hence arose the inquiry to what extent we might rely on 

 the future produce of our coalfields. Professor Hull and others made 

 estimates of the total quantity of accessible coal in the United King- 

 dom, and Sir William Armstrong, in his address at the British Asso- 

 ciation in 1863, gave prominence to the subject, pointing out that the 

 problem to be solved is not how long our coal will endure before 

 there is absolute exhaustion, but how long those particular seams will 

 last which yield coal of a quality and at a price to enable our country 

 to maintain her supremacy in manufacturing industry. Jevons 

 attacked this problem with all the advantage gained from long 

 experience in the collection and management of statistical details. 

 His results were embodied in a treatise, entitled " The Coal Question ; 

 an Inquiry concerning the Progress of the Nation, and the Probable 

 Exhaustion of our Coal Mines." (First edition, 1865 ; second 

 edition, 1866.) Written with clearness, tact and vigour, and pre- 

 senting the matter in a new and interesting light, the work was 

 largely read ; Jevons' conclusions were keenly discussed by journalists 

 and reviewers, and attracted the attention not only of manufacturers 

 and men of business but of politicians and statesmen of the highest 

 order. A Royal Commission was appointed to inquire into the whole 

 question, and Mr. Gladstone used Professor Jevons' calculations in 

 support of his suggestion that a certain portion of the national 

 revenue should be set aside as a reserve fund in payment of the 

 National Debt. 



Problems in applied economics had for Jevons a peculiar attrac- 

 tiveness, because of their bearing on the material welfare of the com- 

 munity. His devotion to abstract studies did not destroy his interest 



