NOTES. CXXXV 



America, Alcide d'Orbigny, Voy. dans 1'Amerique mend. Atlas, PI. VIII. de 

 Ge'ologie spe'ciale, Fig. 1. 



( 54 ) p. 394. Respecting this bifurcation, and the correct names of the 

 eastern and western chains, compare the great Special Map of the Territory of 

 New Mexico, by Parke and Kern, 1851; Edwin Johnson's Map of Railroads, 

 1854; John Bartlett's Map of the Boundary Commission, 1854; Explorations 

 and Surveys from the Mississipi to the Pacific in 1853 and 1854, vol. i. p. 15; 

 and, above all, the comprehensive and excellent work of Jules Marcou, geologist 

 of the Southern Pacific R. R. Survey under the command of Lieut. Whipple, 

 Resume explicatif d'une Carte geologique des Etats Unis et d'un Profil ge'olo- 

 gique allant de la Valle'e du Mississipi aux Cotes de 1'Oce'an Pacifique, p. 113 

 116; also in the Bulletin de la Societe' Geologique de France, 2 e se'rie, t. xii. 

 p. 813. In the longitudinal valley enclosed by the Sierra Madre and Rocky 

 Mountains, in 35 38 N., the single groups, of which the western chain of 

 the Sierra Madre and eastern chain of the Rocky Mountains (Sierra de Sandia) 

 consist, bear special names. To the first-named chain belong (proceeding from 

 south to north) the Sierra de las Grullas, the Sierra de los Mimbres (Wislizenus, 

 p. 22 and 54), Mount Taylor (35 15' N.), Sierra de Jemez, and Sierra de San 

 Juan; in the easternmost chain of the Rocky Mountains may be distinguished 

 the Moro Peaks, the Sierra de la Sangre de Christo with the eastern Spanish 

 Peaks (lat. 37 32'), and the White Mountains which turn north-westward and 

 enclose the longitudinal valley of Taos and Santa FtS. Professor Julius Prbbel, 

 whose examination of the volcanoes of Central America I have already spoken of, 

 has, with much sagacity, developed the indefim'teness of the geographical name 

 Sierra Madre in the older maps; but, at the same time, in a treatise enticed 

 Remarks contributing to the physical Geography of the North- American Conti- 

 nent (Ninth Annual Report of the Smithsonian Institution. 1855, p. 272 281) 

 he has put forward a view to which, after discussing the many now existing 

 materials, I cannot accede: it is to the effect that the Rocky Mountains are by 

 no means to be regarded as a continuation of the Mexican highland in the 

 tropical portion of Anahuac. Uninterrupted mountain-chains, as in the Apen- 

 nines, the Swiss Jura, the Pyrenees, and a great part of our Alps, are not, 

 indeed, to be found running from south-south-east to north-north-west between 

 the nineteenth and the forty-fourth parallels of latitude, from Popocatepetl in 

 Anahuac to north of Fremont's Peak in the Rocky Mountains ; but the enormous 

 general elevation of the surface, which increases more and more in breadth 

 towards the north and north-west, is continuous from tropical Mexico to Oregon ; 

 and on this swelling high plain, which is the primary and principal geological 

 phenomenon, single groups of mountains rise over fissures which have taken 



