122 THE POPULAR SCIENCE MONTHLY. 



Professor Hall himself says of the rationale of the system of no- 

 menclature under which the New York surveys were conducted, and 

 which has served as the basis of the Western surveys : " Since there 

 was no possibility of identifying the individual rocks and groups of 

 strata with those of Europe, as described, the New York geologists 

 were compelled to give names to the different members of the series ; 

 and since the sandstones, limestones, slates, and shales are so similar 

 in different and successive groups, it was impossible to give descriptive 

 names which would discriminate the one from the other. Therefore, 

 local names were proposed and adopted ; as, for example, Potsdam 

 sandstone, Trenton limestone, Niagara limestone, and Niagara shale 

 (the two latter, with subordinate beds, making up the Niagara group), 

 the Medina sandstone, the Onondaga salt group, the Hamilton, Port- 

 age, and Chemung groups, thus giving typical localities of the rock 

 instead of descriptive names. This method or system of nomenclature 

 leaves no possibility of mistake or confusion which might arise from a 

 different appreciation of descriptive terms. The typical locality al- 

 ways remains for study, compai'ison, and reference, and there need be 

 no difference of opinion or discussion as to what was intended by the 

 use of any one of the terms. The progress of geological science in the 

 country is greatly indebted to this system of nomenclature, and to 

 the absolute working out of the succession of the groups, and the 

 members of the same, to which it has been applied." The system 

 was adopted by a vote of the Geological Board. 



The geologists of the survey were accustomed to meet once a year 

 in the Capitol of the State, to compare notes. " The comparison of ob- 

 servations and interchange of views led to the opening of correspond- 

 ence, by a formal resolution of the New York Board, with other 

 geologists, especially with those engaged in State surveys, of which 

 several were ihen in progress. This correspondence led to an agree- 

 ment for a meeting of geologists in Philadelphia in the spring of 1840, 

 and this assemblage, of less than a score of persons, led to the organi- 

 zation of the Association of American Geologists, which, at a later 

 period, on the occasion of its third meeting, added the term Natural- 

 ists ; and, finally, by expanding its title, it became the American 

 Association for the Advancement of Science." Professor Hall was 

 president of this association, under its present title, at its Albany 

 meeting in 1856. 



The general results of Professor Hall's comparative studies in the 

 "West are given in the third volume of the "Paleontology," and more 

 fully in the first volume of the " Report on the Geology of Iowa," 

 where he was engaged in the survey, with Whitney and Worthen. 

 To this survey he contributed a memoir on the paleontology of the 

 State, as he did to the survey of Wisconsin ; and some of the fruits of 

 his paleontological labors may be found embodied in the geological re- 

 ports of several other States. He declined to take the direction of the 



