372 The Loess of North America. [May, 



contains the most finished treatment of the Iowa loess, and inci- 

 dentally that of Missouri and Nebraska, which has come under 

 notice. The last elaborate study, to which it is here necessary to 

 make reference, is contained in the " Sketches of the Geology and 

 Physical Geography of Nebraska," by Professor Samuel Aughey, 

 which is, mainly, so far as the loess is concerned, an extension of 

 his previously published paper in the report of the Hayden sur- 

 vey above mentioned. 1 



From these facts it will have been gathered that the loess is of 

 wide distribution in the great central basin of the United States, 

 to which it seems wholly confined. It is found in the States of Ohio, 

 Indiana, Michigan, Iowa, Kansas, Nebraska, Illinois, Tennessee, 

 Alabama, Mississippi, Louisiana, Arkansas, Missouri, Kentucky, 

 and in the Indian Territory ; but in every instance is apparently 

 confined to the higher lands along the larger streams. Its super- 

 ficial extent is greatest in Nebraska, where, according to Aughey, 2 

 its area is three-fourths that of the State, or 56,994 square miles. 3 

 In Iowa its superficial area is estimated by White 4 at about 

 5000 square miles, but his calculations included only those sec- 

 tions along the Missouri, inasmuch as he was evidently unac- 

 quainted with its existence in Central Iowa, and in the eastern 

 portion of the State. Its area appears to be next greater in 

 Missouri, which is, indeed, but the southern extension of the 

 Iowa and Nebraska deposit. In most of the other States where 

 it occurs its area is comparatively small. 



Physical characters, — Observers agree, in the main, with refer- 

 ence to the physical features of this formation. Its material is 

 exceedingly fine, very silicious as proven by numerous analyses, 

 ashy color with slight yellowish tinge — normally ; and often 

 highly calcareous. In all these respects it agrees entirely with 

 published descriptions of foreign loess. In situ it presents a re- 

 markably homogeneous structure, usually appearing in massive 

 walls without, or with but faint, lamellation, the latter feature be- 



in- biblin-raphy 

 'Sketches, &c. 

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