490 REPORT OF NATIONAL MUSEUM, 1904. 



vey .stratigraphy based upon organic remains was ever uppermost. 

 In the case of the Rogers reports quite the reverse is true, the physical 

 side preponderating over everything else. While the value of fossils 

 in determining the relative age of strata was recognized, yet out of the 

 entire 1,631 pages but 20 are devoted to invertebrate paleontology 

 and 47 —by Lesquereux — to a description and discussion of the fossil 

 flora of the Coal Measures. Naturally, many of the results given in 

 these reports and the opinions expressed had found their way into 

 print several years earlier, particularly through the publication of the 

 American Association of Geologists and Naturalists. Especially was 

 this the case with the results relative to Appalachian structure. 



Rogers was aided by a considerable corps of assistants, many of 

 whom afterwards became noted in the same lines of work. In 1836 

 these were John F. Frazer and dames C. Booth: in 1837, Messrs. S. S. 

 Haldeman, A. McKinley, C. B. Trego, and J. D. Whelpley. with 

 Dr. R. E. Rogers as chemist. In 1838 Messrs. H. D. Holl, J. T. 

 Hodge, R. M. Jackson, J. C. McKinney, P. W. Schaeffer, T. Ward, 

 and M. H. Boye were added to tin 1 force. In 1839 J. Peter Lesley 

 and Doctor Henderson were added in place of Messrs. Whelpley and 

 McKinney, who resigned. In 1840 the personnel was essentially the 

 same. In 1841 it was reduced to Messrs. McKinley, Holl, Jackson, 

 Lesley, Boye. and Doctor Rogers. In 1851 the geological assistants 

 were Prof. E. Desor and W. B. Rogers, jr., Peter Lesley and A. A. 

 Dalson serving as topographers. 



The first volume of these reports treated of the metamorphic rocks 

 and the Paleozoic strata. The second volume began with a discussion 

 of the coal basins of the State, to which over 600 pages were devoted. 

 Some 3o pages were devoted to a discussion of the rocks of the Meso- 

 zoic red sandstone series, which was followed by a discussion, first 

 upon the igneous rocks and minerals with special bearing upon their 

 economic value; second, the conditions of the physical geography 

 during the laying down of the Paleozoic strata of the United States; 

 third, the organic remains of the State; fourth, the laws of structure 

 of the more disturbed zones of the earth's crust; fifth, the classifica- 

 tion of the several types of petrographic structure illustrated in the 

 Appalachians; sixth, the coal fields of the United States and British 

 provinces, with their chemical and physical characters; seventh, the 

 method of searching for, opening, and mining coal, as pursued in 

 Pennsylvania; eighth, foreign coal fields and coal trade and statistics 

 of the iron trade. 



The liontossiliferous rocks underlying the old Paleozoic were classi- 

 fied as Hypozoic or true metamorphic and Azoic or semimetamorphic, 

 the Hypozoic including the true gneisses and crystalline schists, and 

 the Azoic or semimetamorphic strata * ' various coarse talcoid and 



