696 THE JOURNAL OF GEOLOGY. 



graphical researches in the Northwest. Incidentally he aided 

 greatly in determining some parts of its geology. It was through 

 him that T. A. Conrad obtained fossils from the lead-bearing 

 formations of the Upper Mississippi by which he, first of all, cor- 

 rectly assigned that limestone to the age of the Trenton of New 

 York. 1 Professor James Hall, but little later, examined it in 

 the field, and came to the same conclusion. 



The chief event connected with the territorial investigation 

 of the geology of Minnesota was the survey of D. D. Owen, 

 extending from 1847 to 1850, which also covered much contig- 

 uous territory. This survey had the resources and the corps of 

 men which enabled it to pronounce finally on some of the mooted 

 questions of the geology of the Upper Mississippi valley, and it 

 was continued long enough to complete at least a reconnoissance 

 of a large area. Its fine quarto volume, 2 published at Philadel- 

 phia by Lippincott, Grambo and Co., contains, besides the report 

 of Dr. Owen, reports by J. G. Norwood, B. F. Shumard, C. 

 Whittlesey and R. Owen. It embraces also a memoir by Joseph 

 Leidy on the extinct mammalia and chelonia of Nebraska Terri- 

 tory, and several valuable appendixes. Dr. Owen's other assist- 

 ants were J. Evans, B. C. Macy. A. Litton, G. Warren, H. 

 Pratten, F. B. Meek and J. Beal. From this report may be said 

 to date the systematized geology of the state. It laid accurately 

 a broad base on which all future geologists of the state must 

 build. About this time the New York State survey was in vig- 

 orous action, and some of its results had been published. Hall, 

 Conrad, Emmons, and Mather, with Hitchcock of Massachusetts 

 contributed indirectly to the final conclusions at which Dr. Owen 

 arrived. The form of the volume is similar to that of the final 

 report of the New York survey, but its breadth of scope is 

 greater and its typographic execution superior. Its illustrations 



1 Observations on the lead-bearing limestone of Wisconsin and descriptions of a 

 new species of trilobites and fifteen new Silurian fossils. T. A. Conrad. Proc. 

 Acad. Nat. Sci., Philadelphia, Vol. I., 1841-43. 



2 Report of a Geological Survey of Wisconsin, Iowa and Minnesota, and incidentally 

 of a portion of Nebraska territory, by David Dale Owen, United States geologist, 

 1852. 



