MEMORIAL OF H. S. WILLIAMS 49 



mations along the shores of Cayuga Lake, at the head of which young 

 Williams lived. It is possible that had not this report been published 

 when it was Williams would not have become a paleontologist. Many of 

 the superb earlier geological reports of Illinois, Ohio, and Pennsylvania 

 were published at this time or had but recently appeared. Cope was de- 

 scribing his wonderful discoveries of fossil fishes, reptiles, and mammals 

 from the West, and Marsh was well started on his work. Moreover, Wil- 

 liams was a student of James D. Dana, then at the height of his fame and 

 the most eminent geologist of his generation. It was, however, a time of 

 "species-making, '' and perhaps nothing shows better the fine quality of 

 Williams' mind than the fact that, notwithstanding the precedent estab- 

 lished by the eminent geologists of his impressionable years, he invented 

 a new method of stratigraphic study. 



When Professor Williams began his scientific work, it was held that 4 

 distinct set of fossils characterizes each geological formation, but he sooii^ 

 learned that there are exceptions to this important rule. In studying the 

 Devonian formations about Ithaca, he found that the so-called charac-' 

 teristic fossils of the Hamilton formation, for example, also occur in 

 certain beds in the Ithaca; that in the Ithaca Group there is, "first, a 

 Portage fauna, then the Ithaca fauna; third, the Portage fauna again, 

 and finally Chemung capped by the Catskill and Carboniferous.'" This 

 discovery, fundamental as it is, was not immediately welcome to all pale- 

 ontologists, because, as one said, "How is one to be sure of the age 6i smf' 

 formation if one can not depend on the characteristic fossils?'*, Mis 

 practical inconvenience at first prejudiced his colleagues against his 0^7.. 

 servations, but the principal is now an accepted dictum of paleontology/ 



Williams' chief permanent contributions to the principles of paleon- 

 tology were the result of a method of collecting which he appears to have 

 originated and which requires great patience, care, and time. J^ ,j/ j^.' 



In collecting fossils from a section a careful and full examination is 

 made, if possible, of every foot of the section from bottom to topy and 

 where any change in the faunal content is noticed a separate field number 

 is given to this faunule. If when studied carefully in the, laboratory it is 

 found that some of the faunules of adjoining beds contain faunules so 

 closely alike as to signify practically the same set of species,, associated 

 in the same biological equilibrium of relative abundance, tlie}^ are grouped 

 together. ^¥hen collections made in this way from a number of sections 

 near enough to each other are studied, some of the faunal zones can be 

 identified in the different sections. It was by this method that his theory 

 of the "shifting of faunas" and of "recurrent faunas" was demonstrated. 



IV— Bull. Geol. Soc. Am.. Vol. 30, 1918 



