AMERICAN GEOLOGY DECADE OF 1840-l*4'i. 



411 



In 1817 Doctor Owen was again employed by the Treasury Depart- 

 ment, under immediate supervision of General Land Commissioner 

 R. M. Young, to make surveys in the Chippewa district of Wisconsin 

 d.d. Owen's work in and the northern part of Iowa. The region lies between 



the Chippewa District , , 



and in Wisconsin, 4:3 and 4 i north latitude and 89 and 94 longitude 



Iowa, and Minnesota, ,. , ^ • i , i 



1H47 1851. west oi Cireenwich, embracing about 4n,ooo square 



miles and, as shown on the map (fig. 45), comprising that portion of 

 the country ''lying chiefly east of the upper Mississippi above Lake 

 Pepin and extending north to Lake Superior.*" Incidentally, there 

 was included a portion of Iowa "stretching north from the northern 

 boundary of the geological survey of 

 1839 as far as the St. Peters River, 

 and also a tract of country north of 

 the Wisconsin River." 



As in the previous survey, the 

 time was limited, only the summer 

 and autumn of 1847 being devoted 

 to field work, the report, printed in 

 form of Senate Document No. 57 

 of the first session Thirtieth Con- 

 gress, bearing the date of Apri 1 23, 

 1848. It comprised 134 pages, with 

 one geological map, 23 lithographic 

 plates from drawings by Doctor 

 Owen, and 13 colored plates of sec- 

 tions. Some of these last were 

 beautiful combinations of sections 

 and perspective landscapes, and give 

 at a glance a general idea of the 

 surface features as well as the 

 character and dip of the underlying 

 rock masses, such as is randy ex- 

 celled. (See Plate 19, from his sec- 

 tion 5.) Even when one considers 



that, as Owen states, the working time of the members of his corps 

 was from twelve to fifteen hours a day, still one wonders that so much 

 was accomplished and presented in such good form. Though a detailed 

 geological survey was made of only about thirty townships west of the 

 fourth principal meridian on Black River and sixty townships on the 

 St. Croix, sufficient data was obtained to enable him to lay down with 

 approximate accuracy the general I tearing and area of the principal 

 formations of over two-thirds the area above noted. He showed, also. 

 that both the upper and lower magnesian limestone, were lead-bearing, 

 and that there existed in Wisconsin two, if not three, trap ridges simi- 

 lar to those of Michigan, and which, like the last, "hold out a prospect 

 of productiveness. " 



Fig. 45. — Map of areas surveyed by D. D. Owen 

 in towa, Wisconsin, and Illinois in 1839, and 

 the Chippewa Land District in 1S47. 



