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



The cenological* and hypsometrical features were made out 

 during the progress of the present investigation. In the pro- 

 jection of the contours, as well as in the construction of the 

 profile, use was made of all measured railway, roadway and 

 street elevations within the area shown. These data were 

 supplemented by observations and estimates made on the 

 ground and from the dome of the State capitol; from which 

 point nearly the whole area is distinctly visible. Neither the 

 contours nor the profile are, accordingly, strictly accurate, 

 though in a general way they are reliable. 



It may be explained 'that in this latitude in Iowa the drift is 

 everywhere superficially modified to some extent; the upper 

 portion being fine, homogeneous, free from bowlders and peb- 

 bles but sometimes containing calcareous nodules, and loss-like 

 in structure, aspect and topographical configuration, but grad- 

 uating imperceptibly into unmod t within a few 

 feet below the surface. The term "drift" is herein applied 

 only to the upper till, i. e., to the glacial deposit overlying the 

 forest bed. The lower till has not been seen within 'the" area 



The cartography and the preparation of the cuts are the 

 work of the senior author ; the determination of, and remarks 

 on, the fossils enumerated are by the junior author; while the 



East of Four Mile creek lies a gently undulating plain of 

 .litly modified superficially, but exhibiting the eharao- 

 t^nstic drift topography. On the west rises a prominent ridge 

 capped with loss at its southern end but exposing drift in 

 ravines and road-cuttings, formed of fine stratified sand to a 

 oepth of at least fifteen feet in its medial portion, and exposing 

 only drift with rounded and worn erratics cropping out on its 

 summit to the northward. It probably has a nucleus of Car- 

 »>n I' n>us strata, overlain throughout bv drift; the sand and 

 loss being superimposed upon the drift stratum. This ridge is 

 !y analogous to the asar of eastern Iowa. West of it 

 lies a uniform plain formed of drift with little superficial modi- 

 fication, so low and level as to be almost without natural diain- 

 aue. As a broad trough, this plain connects the angles in the 

 v; , lll '/ v o| the Des Moines river above and below the confluence 

 of the Raccoon in so marked a manner as to have given rise to 

 the general (but erroneous) popular impression that it is an 



Huviiitik' ;nnl lacustral deposits. 



