178 Wisconsin Academy of Sciences^ Arts and Letters. 



the lake are developed for a distance of six or seven miles through the 

 south part of Tp. 42 N., E. XIII E., and the central part of Tp. 41 N., R, 

 XIII E. The highest part of the beach line, or beach lines, for a series of 

 ridges is developed, is about 60 feet, occasionally 61 feet above Lake Michi- 

 gan. In the vicinity of the Chicago river, the elevation gradually decreases 

 to the level of the river bank, which is about 40 feet above L,ake Michigan. 

 These gravel deposits of the beach line, or of succeeding beach lines which 

 lap onto its eastern face, have an eastward extension on the north side of 

 the river, so that when we cross the river to find the beach line on that side 

 we must go nearly two miles up the stream to catch it. This protrusion of the 

 sands and gravels on the north side of the stream indicates that at the time 

 this beach was forming the transportation of sand and gravel was southward 

 along the shore, and that the current from the Chicago river, which opened 

 into the lake at the point represented by the position of the beach line on 

 the south side of the river, carried the material lake ward which was 

 brought down by the slow moving lake current from the north. This ex- 

 tension is not in the form of a delta built up at the debouchure of the river 

 •into the lake — but lies wholly on the north side of the river valley. More- 

 over, to make it still more evident that it was the lake and not the river 

 which contributed the great bulk of the beach deposit which skirts its north 

 bank, we find that the river valley above the point where it entered the old 

 lake has very little assorted material, such as would accumulate above a 

 delta. The beach appears on the south side of the river in the south part 

 of Sec. 19, Tp. 41, R. XCII E. It has here a very different aspect from that 

 immediately across the river, being a low sea cliff, 6 — 15 feet in height, 

 with occasional deposits of beach gravels and sands along its front. The 

 terrace or sea cliff made by the lake, is crossed by the Wisconsin division of 

 the Chicago and Northwestern railway, at Norwood Park. The profile of 

 this road shows that the base of the sea cliff has an elevation of 45 feet, and 

 the top an elevation of sixty feet above Lake Michigan. 



At the point where the Chicago, Milwaukee & St. Paul railway crosses 

 the cliff, in Sec. 32, Tp. 40, R. XIII E. , the base has an elevation of 42 feet and 

 the top 66 feet. The Omaha division of the Chicago & Northwestern railwaj 

 crosses it at Oak Park, with an elevation of 38 feet at the base and 49 feet 

 at the top of the cliff, and a mile further south the Wisconsin Central rail- 

 road (grosses a beach deposit with an elevation of 41 feet at the base and 49 

 feet at the top. 



The sea cliff phase extends only to Oak Park, a village on the east bank 

 of the Des Plains river. The sea cliff passes through the east part of the 

 village to the vicinity of the Chicago & Northwestern railway, where 

 beach gravels conceal it, and we find here an extension of the beach gravel 

 down the east side the Des Plains river, similar to that extension down the 

 north side of the Chicago river. The gravel extends south from Oak Park, 

 in the form of a ridge, or bar, 20 to 40 rods in width and 10 feet or more in 

 height, for about two miles to the south part of Sees. 13 and 14, Tp. 39' 



