NATIONAL, ACADEMY BIOGRAPHICAL MEMOIRS VOL. VIII 



REPORTS AND FOUOS. 

 V*"" 



The many geological studies published in annual reports, 

 monographs, bulletins, and folios exhibit admirably the work 

 of individual members of the Survey; but they reflect credit 

 also on the Director, who knew how to select good associates, 

 and who wisely trusted them with great responsibilities and 

 gave them great liberty of action. Powell, indeed, had so 

 much native capacity that he never hesitated, as a weaker 

 Director might have done, to employ men who knew more 

 geology than he did himself. The "Correlation Papers," pre- 

 pared according to a general plan by eleven specialists under 

 Gilbert's supervision to summarize knowledge regarding suc- 

 cessive geological periods, contributed greatly to a broad un- 

 derstanding of large problems; and these papers constitute a 

 thoroughly characteristic product of Powell's administration. 

 The annual volumes giving statistical summaries of mineral 

 resources also deserve special mention as initiated under 

 Powell's direction. They are probably as accurate as possible 

 under the conditions of their preparation, but they are prob- 

 ably not so accurate as they appear to be. The geologic folios, 

 containing sheets of the geological map of the United States 

 which the Survey had been instructed to prepare, are based on 

 a uniform and comprehensive plan, and exhibit, like the topo- 

 graphic maps, Powell's remarkable foresight and breadth of 

 view. The plan for the publication of the folios was carefully 

 discussed in several conferences, of leading geologists ;. careful 

 debate was given to the general explanatory text of the cover, 

 to the scheme of coloring, so admirably carried into effect by 

 the engraving department of the Survey, and to the liberal 

 presentation of topography, geology, structure, and economic 

 features on separate sheets, all this being told in the Tenth 

 Annual Report (1888-1889). The first geologic folio was 

 issued in 1892, thirteen. years after the establishment of the 

 Survey; later folios show marked improvement in various 

 directions, the text in particular becoming more elaborate and 

 pictorial illustrations were abundant ; but the original plan is 

 still followed, except for the inevitable departure from the 

 intention that the text should be "so prepared as to be intelli- 



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