414 W. J. If c Gee — Geology of the Mississippi Valley. 



capped, in the large majority of cases, by the loss-like member. 

 The rather hurried examination given to those of the level plains 

 of Illinois failed to reveal any order or system in their distribution. 

 They begin to appear at intervals about 40 or 50 miles north 

 of the southern limit of the unmodified upper drift (number three), 

 and dot the surface to the southward, increasing gradually in extent 

 and number, but finally diminishing in altitude, and at last becoming 

 merged in the loss there forming the uppermost deposit. These 

 elevations have in some cases been found to be wholly independent 

 of the subjacent members ; and it is suspected that, where they are 

 not coordinated with the configuration of the basalt rocks, they are 

 always so. 



Terraces are rare, and never prominent. There are none which, 

 in the judgment of the writer, owe their origin to continental oscilla- 

 tions in level, or even to a gradual elevation of the land. The two 

 principal surface deposits, too, are spread over the older rocks 

 uniformly, on hills and in valleys alike, independently of altitude. 



Bodies moutonnees occur in many localities, but their materials are 

 usually too friable, and their surfaces too greatly weathered, to 

 exhibit strias. Ground and polished rock-surfaces, which are so 

 often seen in broken and hilly countries, are almost unknown here ; 

 but it must be remembered that extensive surfaces are very seldom 

 exposed, being ordinarily deeply covered with drift. Neither have 

 the " striated pavements " of Hugh Miller been observed. 



Sections. 



To the working geologist a few actual sections will be of as great 

 value as the more general description. The following are taken 

 almost at random from the writer's notes. 1 



The relations of some of the members could only be clearly 

 exhibited by means of sketch sections ; and hence no effort has 

 been made to select those containing such members. All were 

 observed in wells. 



1. A well at WoolanCs Station, Stephenson county, Illinois. 



Soil _ 2 feet. 



Coarse yellow clay, with boulders and chert 18 „ 



Blue clay, clean and unstratified 25 ,, 



Gravel and sand, stratified, on rock 5 „ 



Total 50 „ 



2. Ilendota, Illinois. 2 



Yellow clay, with boulders 12 feet. 



Blue clay, sometimes sandy 55 ,, 



Gravel 3 inches 



Blue clay, laminated and sandy 7 „ 



"Water-bearing gravel reached. — 



Total 74 „ 



A sample of the blue clay from 60 feet below the surface contains 



1 In the paper read before the American Association is a table of eighty-three 

 sections in North-eastern Iowa. 



2 Communicated, with the following, and with samples from different depths, by 

 Dr. J. D. Moody. 



