AMERICAN GEOLOGY DECADE OF 1850-1859. 449 



mond and one near Raton Mountains, in New Mexico, as Lias or 

 Jurassic (blue). A band of Keuper was also represented as extending 

 from the eastern end of the south shore of Lake Superior quite across 

 the Co tea u des Prairies to the ninety-eighth meridian. A continuous 

 band, colored as composed of granite porphyry, syenite, greenstone, 

 gneiss, mica-schist, etc., was represented as extending from below the 

 twenty -fourth parallel in Mexico northward to the great bend of the 

 North Platte in Wyoming, where it was overlain by Silurian, Devo- 

 nian, Coal Measures, and Keuper strata, the latter flanked on the north 

 by a broad band of "copper trap/' Here again the series extended 

 westerly to the edge of the map and northeasterly to a point about 

 midway between Mandan and the Little Missouri River in Dakota. 



This attempt on the part of Marcou was certainly commendable, 

 requiring courage as well as judgment. Unfortunately, Marcou does 

 not seem to have used discretion in all cases in the selection of his 

 authorities, and made altogether too sweeping generalizations, often 

 in direct contradiction of facts made known by other workers. 



In 1855, 1858, and again in 1872 Marcou published in German}^ and 

 France other editions of his map, in which he comprised the whole 

 country from the Atlantic to the Pacitic Ocean. Perhaps the most 

 striking feature of these issues is the enormous area of country west 

 of the Missouri at Iowa and extending almost to Great Salt Lake and 

 the Colorado River in Arizona, colored as red sandstone (Trias), with 

 broad intercalations of Jurassic. This feature is the same on issues 

 of both 1855 and 1858, although in the map of 1853 he colored the 

 same area (at least as far as this map extended) Cretaceous, Tertiary, 

 :ind Quaternary. In the edition of 1855 the entire west coast of Cali- 

 fornia south of Humboldt and as far down as Monterey was colored as 

 occupied by eruptive and metamorphic rocks, while broad belts in the 

 interior, along the courses of the main rivers, were colored as Tertiary. 

 In the edition of 1858 this was in part corrected, the Tertiary being 

 extended to the coast. 



The various editions of these maps, on account of the errors men- 

 tioned and numerous others perhaps even more inexcusable, though 

 less conspicuous, were severely criticised by American geologists, a 

 particularly harsh review of the 1853 map being given b\ T James Hall 

 in the American Journal of Science for March, 1854, and of that of 

 1855 by W. P. Blake in the same journal for November, 1856. 



During 1853 numerous expeditions were sent out by the War 



Department for the purpose of exploring routes for 



su^y C s^ C 853-i™sl tne proposed railroad from the Mississippi Valley to 



the Pacific coast. These were in all cases under the 



immediate command of officers of the Army, but to nearly all one or 



more naturalists or geologists were attached. 



NAT mus 1904 29 



