448 



REPORT OF NATIONAL MUSEUM, 1904. 



Jules Marcou's 

 Geological Map of 

 the United States, 



1853. 



In an article communicated to the Natural History Society of 

 Montreal in I860, Dawson claimed to recognize ''among the partially 

 metamorphosed sub-Carboniferous rocks of Nova Scotia, formations 

 ranging from the Middle Silurian to the Lower Devonian, inclusive, 

 bat of a more argillaceous and less calcareous character than the series 

 occupying this position in the mainland of America." The granites 

 (intrusives) he regarded as of newer Devonian age, and the Arisaig 

 series as representing "the upper part of the Middle Silurian, proba- 

 bly with a part of the Upper Silurian, a position much lower than that 

 assigned to it in my Acadian Geology."" 



In 1853 Jules Marcou, a Frenchman who had come to America in 

 1848, published a geological map of the United States and the British 

 Provinces of North America, with 92 octavo pages of explanatory 

 text, two geological sections, and eight plates of the 

 fossils which characterize the formations. The map. 

 which was colored by hand, extended as far west as 

 the one hundred and sixth meridian, and the geological sections, not 



colored, extended, the first from the Atlantic 

 Ocean at Yorktown, Virginia, to Fort Lara- 

 mie, Nebraska, and the second from Lake 

 St. Johns in the Hudson Ba} T Territory to 

 Mobile, Alabama. 



The author adopted the formation names 

 established by M. de Verneuil and Murchi- 

 son, in order to render possible a satisfactory 

 comparison with the existing geological 

 maps of England, Germany, Russia, Scan- 

 dinavia, and Bohemia. The divisions Cam- 

 brian and Taconic, however, were not recog- 

 nized, since, in the opinion of the compiler, 

 the}^ "ought to disappear from geological 

 classification, for they give two names to the 

 metamorphic rocks, of which they are integrant parts, in all regions 

 where these beds have been observed."" 



Perhaps the most striking feature of the map, at least that in which 

 it differs the most from those of later date, lay in the enormous devel- 

 opment of the Devonian, which is made to occupy a large portion of 

 southern New York, as now, and to extend thence in a continuous, 

 broad, but gradually narrowing band southwesterly to near Tusca- 

 loosa, in Alabama. A continuous belt was also indicated as extending 

 from the east side of the south end of Lake Michigan westerly nearly 

 to the Missouri River. The brown Triassic sandstones of the Eastern 

 States were colored as Keuper (yellow), and the belt west of Rich- 



Fig. 58. — Jules Marcou. 



" This statement regarding the Taconic is a little surprising when one considers 

 the part Marcou played in the subsequent controversy (see p. 659). 



