206 McGee and Call — Loss of Des Moines, Iowa. 



South ward" from the river bluffs the bowlder-bear- 

 ing deposit merges into the superficially modified drift extend- 

 ing to the Three Eivers, and the general altitude gradually 

 es. Ascending the Eaccoon the elevated range of bluffs 

 iddenly dies away at the westernmost Four Mile creek; 

 and above are the more gentle slopes characteristic of drift areas 

 — the slope here being toward, instead of away from the river. 



Summing up the predominant physiographical features of 

 the region under consideration, it appears (1) that the Des 

 Moines and Eaccoon rivers have avoided uniform plains and 

 have corraded their channels through the most elevated plateau 

 •of sedimentary strata existing within many miles; and (2) that 

 there has been an unusual aceumulati >n <>! < > uiternary deposits 

 over this plateau about the confluence of the rivers. 



These features conform to laws which the senior author has 

 found to obtain over much of eastern Iowa; for not only do 

 the North Maquoketa, South Maquoketa, Buffalo, Wapsipinni- 

 con, Cedar and Iowa rivers avoid low-lying plains and seek 

 elevated plateaus and ridges of both sedimentary rocks and 

 quaternary deposits in many localities, but the general course 

 of all these rivers is at right angles to the mean slope of the 

 surface which they drain. 



II. 



The following are a few only of the sections examined. 

 Each is located on the map, and numbered as in the text. 

 ade is to the top of the section. The probable error 

 in altitude refers to the city datum of low water at the conflu- 

 ence of the Des Moines and Eaccoon rivers, which is assumed 

 to be 780 feet above sea level.* In the lists of fossils, species 

 not now living in the vicinity are marked with an asterisk. 



Section 1. 

 S.W. cor. Walnut and E. 9th Sts.— Altitude, 860 ± 2 feet. 

 1. — Loss, light drab, fine, homogeneous, without distinct stratifi- 

 cation, with vertical structure and cleavage, and with two 

 or three irregular zones yielding a profuse calcareous efflo- 

 rescence. It contains tolerably ahundant lossd<indchen,+ 

 tubeletB (or slender, irregularh ramifying calcareous tubes), 

 and characteristic loss fossils disseminated throughout. 

 Ten feet. 

 * Gannett ( 1 1 t - . El <\ u- ltd ed 1877, p. 70) gives 779 feet as the low- 

 f Over 2800 loss-kindchen, mainly from sections 1, 2 and 9, were recently 



