AMERICAN" GEOLOGY DECADE OF 1840-1849. 413 



Concerning the red sandstones of the south and west shores of Lake 

 Superior, he wrote: "There is strong- presumptive evidence that they 

 were deposited subsequently to the Carboniferous era." His evi- 

 dence, though, was admittedly weak and later was acknowledged to be 

 wholly misleading and insufficient. 



This preliminary reconnaissance ended. Owen was instructed to make 

 a survey of the Northwest Territory, embracing chiefly Wisconsin, 

 Iowa, and portions of Minnesota. The manuscript of his final report 

 of this work was submitted in 1851 and published under date of 1852 

 in the form of a quarto volume of 628 pages of text, with 15 plates of 

 fossils, 19 folding sections, and a geological map. The illustrations of 

 the fossil remains are of particular interest, being medal-ruled on 

 steel, the first of their kind produced in America. 



Owen was assisted in this survey by Doctors Shumard and Litton, of 

 St. Louis; Dr. John Evans and F. B. Meek, of Owensboro, Kentucky; 

 Col. C. Whittlesey, of Cleveland, Ohio; and Messrs. B. C. Macy, Henry 

 Pratton, George Warren, and John Beale, of New Harmony. Indiana. 



To Doctor Leidy fell the work of describing the vertebrate fossils 

 collected by Doctor Evans in the Bad Lands of Nebraska. Among 

 these fossils was the now well-known Oreodon, an animal with grind- 

 ing teeth like the elk and canines like those of omnivorous thick- 

 skinned animals, belonging, as was thought, to "a. race which lived 

 both on flesh and vegetables and yet chewed the cud like our four- 

 footed grazers." 



This work was the first S3^stematic account published of the Bad 

 Lands fossils. The first mammalian remains to be described from this 

 region, it should, however, be noted, consisted of fragments of the 

 jaw of an enormous pachyderm, which were described by Dr. H. A. 

 Prout, of St. Louis, in the American Journal of Science for 1847. 



Owen regarded the gypsum deposits of Dubuque as due to original 

 deposition at the bottom of an ocean, the sulphate of lime having 

 probably been derived during the formation of the rocks and from sub- 

 marine sources. This view is somewhat remarkable when it is recalled 

 that of the total lime salts in solution in sea water, 90 per cent occur 

 in the form of sulphates and would be deposited as gypsum during the 

 ordinary processes of evaporation. 



His views on the origin of the drift were in accordance with those 

 of the leading authorities of his day. The large bowlders he regarded 

 as having been deposited by floating ice and drifted by currents from 

 the north while the country was depressed. The opinion which he 

 had previously expressed (in 1848) concerning the age of the Lake 

 Superior sandstones was in this final report retracted, and he relegated 

 them, on stratigraphic evidences only, to the Potsdam formations, 

 which is in accordance with the prevailing opinion of to-day. 



