84 ILLINOIS ACADEMY OF SCIENCE 



most abrupt face of Monk's Mound and from them to take 

 samples of the earth of which it is constituted. The bluffs of 

 the river, two miles away, and the surrounding mounds, were 

 similarly examined and the materials compared. The top of 

 Monk's Mound (from the 500 to 490 foot contour) consists 

 of earth similar to the loess on the bluffs at similar levels 

 about two miles further east. It contains less calcareous ma- 

 terials than does the bluff earth, since the overlying soils on 

 the bluffs, rich in lime, are wanting, and it has been thor- 

 oughly leached. Thirty feet farther down (from 460 feet 

 to 450 feet contour) the earth is richer in sand and at one 

 place a stratified bed of sand is in evidence. Twenty feet be- 

 low this (from 430 feet to 420 feet contour) the material 

 is a tough blue clay. The soil composing the floor of the 

 "American Bottoms" is a loam containing sand, lime and 

 clay. 



The fact that the constituent materials are different at dif- 

 ferent levels in the large mound; that they are the same at 

 the same elevation in mounds a mile apart and in the bluff two 

 miles away ; that they are stratified, and that they are in differ- 

 ent order than they would be if heaped up by human labor, all 

 show beyond doubt that Monk's Mound and neighboring 

 mounds are natural remnants of waterborne glacial materials 

 which once filled the valley 



Further at an elevation of 485 feet is a bed of fossil hack- 

 berry seeds. These beds and other fossiliferous layers* show 

 that the materials containing them were deposited by water. 



Again, the location and physiography of the mounds clearly 

 indicate their origin. They form the divide or water shed 

 between Cahokia Creek on the north and the small streams 

 flowing westward along the southern side. The contours of 

 the mounds are typical of water carved land. 



Finally it is to be doubted that Indians who were kept busy 

 with the struggle for existence and who were naturally disin- 

 clined towards unnecessary work would erect a great mound 

 in a region where nature had already produced an abundance 

 of rounded hills and bold bluffs. 



All of which shows that Monk's Mound was not built by 

 man. 



Dr. Snyder reports the finding of Physa heteorostropha, Limnea humilis, Helix 

 concava and striatella, and Succinea obliqua. 



The writer found a number of shells which were determined by Dr. Pillsbury of 

 Philadelphia to be Pyramidula perspectiva ; Succinea Grosvenori Lea; Helicina occulta 

 Say., Physa gyrina. 



