itevieios— Cretaceous Series of Upper Missouri. 425 



blocks. In tins position they are much more stable than on posts, 

 although anything resting upon the overflow is unstable. It is the 

 cheese-pitch, full of water, and containing more or less gas, buried 

 beneath these surface accidents, that has flowed and still flows. 



Although a large amount of clay and vegetable debris fills the 

 interstitial spaces of the rough surface of the asphalt, the vegetation 

 is not confined to such surfaces, but seems to flourish equally well 

 upon the bare pitch, the roots penetrating the pitch without the 

 slightest difficulty, except where it had been converted by melting 

 into iron-pitch. There is also considerable coke where the fires 

 have been hottest. All of these impurities are carefully excluded 

 from the pitch that is rained, both for boiling and for shipment 

 in the crude state, by all of the men employed by the difterent 

 companies in extracting it. This selection is not difficult, as the 

 appearance of the iron-pitch is very different, and the amount very 

 small, as compared with the pure or cheese-pitch. 

 {To be continued in our next Number.) 



lE^ DE "V^ I IE -VT- S. 



s 



•The Cretaceous Series of tue Upper Missouri; and the 

 Chalk of North America and its Foraminifera. 

 ^-EVERAL interesting and instructive reports are published in the 

 O Iowa Geological Survey, vol. iii. Second Annual Report, 1893, 

 with accompanying papers : 501 pages, with numerous maps, plates, 

 cuts, and photographs. Large 8vo, Des Moines, 1895. There are : 

 1. Cretaceous deposits of the Sioux Valley; by H. F. Bain. 2. 

 Certain Devonian and Carboniferous outliers in Eastern Iowa ; by 

 W. H. Norton. 3. Geological section along Middle River in Central 

 Iowa; by J. L. Tilton. 4. Glacial scorings in Iowa; by C. R. 

 Keyes. 5. Thickness of the Pah^ozoic strata of North-eastern 

 Iowa; by W. H. Norton. 6. Composition of the Iowa Chalk; by 

 S. Calvin. 7. Buried River-channels in South-eastern Iowa; by 

 C. H. Gordon. 8. Gypsum deposits of Iowa; by C. R. Keyes. 

 9. Geology of Lee County ; by C. R. Keyes. 10. Geology of Des 

 Moines County ; by C. R. Keyes. 



I. At pages 101-114 Mr. Bain details the features and measure- 

 ments of the Cretaceous series as seen along the Sioux River, a 

 tributary of the Upper Missouri, forming the northern third of the 

 western boundary of Iowa. Beneath a thick coating of drift and 

 loess, he notes the occurrence (downwards) of— (1) the Pierre shale; 

 (2) Niobrara chalks and soft limestone (locally unconformable on the 

 Sioux quartzite) ; (3) Benton shale; and (4) Dakota sandstones and 

 shales. These formations vary in their thicknesses over this part 

 of America; and here are apparently some 300 or 400 feet thick. 

 They correspond with the description given of this and neighbouring 

 districts by Meek and Hayden (1853-1873), except that the top- 

 most part of the series, namely, that of the Fox Hills (sandstones 

 and arenaceous shales), is not shown on the Sioux River. Mr. Bam 

 points out that the recognized eastward extension of the upper 



