84 THE GEOLOGY OF MINNESOTA. 



[Owen, 1850. 



observe any thing that represented the Maquoketa shales, which separate 

 them in Iowa. The Galena he makes the equivalent of the Utica slate and 

 Hudson River group, which latter also seems to include the Maquoketa 

 shales. He recognized the Devonian formation near the southern boundary 

 of the state along the Cedar river, but he made no note of the Cretaceous 

 within the state. Its exposures are referred by his assistant, Dr. B. F. Shu- 

 mard, either to the Lower Silurian or to the epoch of the drift. Fragments 

 of lignite found in the valley of the "Mankato" river were supposed by him 

 not to have come from the rock in situ within Minnesota, but to have been 

 transported with the drift from the north, perhaps from the beds reported 

 by Dr. Richardson to contain coal on the shore of Great Bear lake, "or from 

 the Cretaceous or super-Cretaceous lignite formations which were observed 

 by Nicollet and others, oif toward the Missouri and Rocky mountains." 



That part of the report which is most valuable to Minnesota was written 

 by Dr. J. G. Norwood. It is also the most voluminous.* The rock speci- 

 mens collected by him, numbered up to 680, are described with care and 

 discrimination, and were probably deposited in the Smithsonian Insti- 

 tution at Washington. They were obtained in the northern and eastern 

 portions of the state, and illustrate specially the northwest shore of lake 

 Superior. The report on the north shore of lake Superior is remarkable for 

 the minuteness of the description of the topography of numerous valleys, 

 and for the correctness of the general views of its geology. Its numerous 

 illustrations are graphic, and, although sometimes aided by idealization, are 

 essentially correct. They show vividly the interstratification of the igneous 

 and sedimentary rocks, and depict numerous remarkably picturesque spots 

 at which both the artist and the geologist willingly linger. His views of the 

 metamorphism of the sedimentary beds by the action of the igneous, were in 

 accord with the current interpretation of crystalline rocks of his day, and 

 were in confirmation of the views of Mr. Mather of the New York state 

 survey, in opposition to those of Mr. Emmons, on the Taconic controversy, 

 although the bearing of his report on that controversy was not mentioned 

 by Dr. Norwood. The frequency and importance of the action of the igne- 



*This valuable report is not mentioned by Dr, T. S. Hunt in his resume of the literature of the crystalline rocks ol 

 America for the second Pennsylvania Survey (Rep. E.) 



tin the ninth annual report of the Smithsonian Institution, where the collections of Dr. Own are catalogued, 

 together with those of Jackson, Locke, Foster and Whitney, no mention is made of those of Norwood. 



