THE GEOLOGIC ATLAS OF THE UNITED STATES 341 



ration ago several of the world's intellectual leaders occupied 

 themselves most laudably in teaching the beneficence of science 

 and its freedom from mystery; today the teaching has become 

 an object lesson through the Geologic Atlas of the United States. 



An example — it may not be invidious to say the finest exam- 

 ple to date — of the " atlas folios " issued by the Survey is the 

 Pueblo Folio, by G. K. Gilbert.* Like the rest of the series, it is 

 a thin folio, 21f by 18? inches,; bound in a moderately stiff ma- 

 nilla paper. The first cover page bears an index map showing 

 the position of the area represented, and also of other published 

 folios, with respect to considerable adjacent territory ; while the 

 second and third cover pages contain an elementary " Explana- 

 tion" setting forth in simple language the principles and methods 

 of topographic mapping, and the classification and conventions 

 used in the geologic mapping. This text is general, equally 

 applicable to all atlas folios, and signed by the Director. Like 

 most of the other examples, the folio proper comprises (1) a pre- 

 liminary descriptive text, followed by (2) a topographic atlas 

 sheet representing the " quadrangle " (or tract) to which the 

 folio is devoted, (3) a geologic map of the same tract, (4) an 

 economic map of the tract showing the distribution and indicat- 

 ing the value of the important resources, (5) a sheet of sections 

 exhibiting the structure of the tract, and (6) special supplement- 

 ary illustrations. In this instance the special illustrations com- 

 prise (a) a lithographic reproduction of a model showing the 

 deformation of the tract during a particular epoch, (b) a map 

 showing the distribution and depth of phreatic water within 

 reach of artesian and pumping wells, (c) a series of columnar sec- 

 tions showing in detail the structure and thickness of the beds, 

 and (d) illustrations of typical fossils and rock-structures. Like 

 other folios of the series (of which this is No. 36), the work is 

 distributed to certain libraries and other depositories, and is 

 sold, on application to the Director of the Survey, for 50 cents. 



The " Description of the Pueblo Quadrangle " forming the au- 

 thorial text of this folio is especially noteworthy as representing 

 the work of one of the foremost geologists of the world in a 

 peculiarly instructive geologic province. It begins with an intro- 

 duction in which the terminology is explained. This is followed 



* Department of the interior | United States Geological Survey | Charles D. Waleott, 

 Director | Geologic Atlas | of the | United States | Pueblo Folio | Colorado. [Index map, 

 list of sheets, etc.] Washington, D. C | Engraved and printed by the U. S. Geological 



Survey | Bailey Willis, Editor of Geologic maps. S. J. Kubel, Chief Engraver | 



ls;iT. 



