IOWA ACADEMY OP SCIENCES. 61 



of glaciated rock in this region, and pointed out that the testi- 

 mony they gave was unanimous as to the southeastern move- 

 ment of the ice sheet. Since then another exposure has been 

 located that seems to bring conflicting testimony. 



This locality is the joint discovery of Mr. Frank Leverett 

 and myself. It is situated on the lot at the northeast corner of 

 the intersection of Court and Prospect streets in the city of 

 Burlington. Some quarrying had been done by blasting out 

 the level rock aoor. Everywhere on the margin of the hole 

 thus formed may be seen the finely striated and grooved sur- 

 face. On the east side a patch, 6x8 feet, was cleaned off and a 

 finely striated surface brought to view. The direction of the 

 stri^, taken with compass and corrected, was S. 79° W. This 

 would indicate an almost due westerly movement, which is in 

 direct variance with that shown by all other discoveries of gla- 

 ciated rock in this region. If direction of strice alone were taken 

 into consideration, then it might be claimed that the ice move- 

 ment in this case also was towards the east. But a close and 

 critical examination shows that all the accompanying phe- 

 nomena point to a westerly trend; e. g., the indicated move- 

 ment of the ice around and over a prominence, and down into 

 and out of a depression. 



This is new and important evidence that the Illinois lobe of 

 the great ice sheet crossed the Mississippi river and invaded 

 Iowa. It will be remembered that I presented a paper on this 

 subject at our last meetitg.^ The evidence on which the claim 

 was based was the presence, on the Iowa side, of boulders of 

 Huron conglomerates. I was convinced that this westward 

 movement was not the latest in this region, but that the ice 

 moving from the northeast was the last to hold possession of 

 the west bluff of the Mississippi; and I so put forward in the 

 paper. Mr. Frank Leverett, who has made an exhaustive study 

 of this question, is of the opinion that the Illinois ice sheet was 

 the last to invade this portion of Iowa, and that the movement 

 extended to some twenty miles west of the river. This recent 

 discovery of glacial scoring certainly strengthens his theory. 

 For it is situated at such an elevation that any ice sheet passing 

 over would be almost certain to leave its impress; and there- 

 fore the strice we now find are very apt to be those made by the 

 latest invasion. 



2Extensiou of the lUinois Lobe of the Great Ice Sheet Into Iowa. Proc. la. Acad. 

 Sci., Vol. II, p. 309. Des Moines, 1895. 



