i9o6] CHANCE— BIOGRAPHICAL NOTICE OF J. P. LESLEY. xiil 



first volume, including especially the essay on " Geological Time,"^ 

 better perhaps than anywhere else we find the impress of his sign- 

 manual ; here are arguments, conceived and developed in a brain 

 accustomed to exact scientific analysis, recorded with the clearness 

 and simplicity of one writing for children, yet with the logic of a 

 master in debate ; the product of genius beyond praise. 



But this great task he was not permitted to finish ; his strength 

 was insufficient, and after publishing two volumes and preparing a 

 portion of the third and final volume (embracing in all over i,8oo 

 octavo pages), he reluctantly delegated to others the writing of the 

 final chapters. 



In 1892 in failing health he removed to Milton, Massachusetts,, 

 where he lived until his death in 1903. 



In addition to his membership in this society he was a corporate 

 member of the National Academy of Sciences, Fellow of the Amer- 

 ican Association for the Advancement of Science, member of the 

 Boston Natural History Society, of the American Oriental Society, 

 of the Academy of Natural Sciences of Philadelphia, of the Oriental 

 Club of Philadelphia, foreign member of the Geological Society of 

 London, associate member of the Societe Geologique du Nord, mem- 

 ber of the Moscow Imperial Society of Naturalists, the Emden and 

 Neufchatel Academies of Science, the Lille Academy of Natural 

 Science, Foreign Honorary member of . the American Academy of 

 Arts and Sciences, member of the Union League Club of Philadel- 

 phia, and honorary member of the American Institute of Mining 

 Engineers. 



The degree of LL.D. was conferred upon him in 1878 by Trinity 

 College, Dublin. 



Aside from his work as state geologist of Pennsylvania, his most 

 valuable contribution to the world of science was the discovery and 

 enunciation of the principles governing the relation of structural 

 geology to topography. He was the father of the science of topo- 

 graphic geology to which he early directed attention by illustrations 

 prepared for the reports of the First Geological Survey of Penn- 

 sylvania of which Henry D. Rogers was the author, and by further 

 elaboration of the subject in 1856 in his '' Manual of Coal and Its 

 Topography," wherein the relation of structural geology to topog- 



