Raised Beaches of Lake Michigan. 183 



line ininniug from the bluffs of the Galvin river valley, north to the lake 

 bluff. Its elevation at the lake bluff is about 55 feet, by aneroid deter- 

 mination, above the present lake level. This probably represents the Up- 

 per beach. 



At several points between these " clay banks" in Sec. 30, Tp. 7 S., R. XX 

 W., and Sawyer in Sec. 3, of the same township, the gravels on the river 

 slope of the till ridge, which passes from the clay banks northward are in 

 the forms of beach lines. They occur at an elevation as great as the track 

 of the Chicago and Western Michigan railroad, which is 55-60 feet at sev- 

 eral points where comparisons could be made. One of the best developed 

 fragments of a beach line may be seen 100 rods or more west of the depot 

 at Sawyer, where it is crossed by a wagon road. No beach lines were ob- 

 served north from Sawyer, which will be included with the Upper beach 

 deposits, but occasionally the slopes of till ridges were coated slightly 

 by gravel at elevations about the same as those of the Upper beach — i. e., 

 — 55 feet or more above Lake Michigan. 



The lake bluffs north from St. Joseph were examined with reference to 

 finding the elevation to which the gravels occur, both in eroded dunes and 

 above till bluffs, but nowhere were any deposits found at a height ex- 

 ceeding 35 feet above the lake. Quite frequently eroded dunes exposed 

 gravel to an elevation of 20 — 35 feet, but this is probably to be classed with 

 the gravels of the middle and lower beaches. 



THE MIDDLE BEACH. 



We find it necessary to explain the general surface features of a tract 

 north of the Chicago river before attempting to give the distribution of the 

 beach lines which border it. There is a till plain lying east of the portion 

 of the upper beach that lies north of this river. Its western border is 30 

 feet or more above the level of Lake Michigan. Tliis till plain has a width 

 of two to four miles, and descends toward the east to an elevation of but 

 10 — 15 feet above the lake. East of this till ])lain there is a prominent beach 

 line rising to an elevation of 30 — 35 feet above Lake Michigan. The plain 

 therefore appears to be bordered by two beach lines, the one on the west 

 being 40 feet more or less above the level of the lake, while that on the east 

 is 30-35 feet. Taking up now the distribution of these beach lines we can 

 best describe the western one as lying along the eastern face of the portion 

 of the upper beach north of Chicago river, differing from it only in eleva- 

 tion, and in having a more easterly extension down the north side of Chi- 

 cago river. The eastern beach line leaves the lake bluff about two miles 

 north of Evanston and passes nearly due south for some seven miles to 

 Rose Hill cemetery. At the cemetery it makes an abrupt turn to a course 

 slightly soutli of west and extends to Bowmanville in Sec. 12, Tp. 40 N., R. 

 XIII E. , where it drops down quite suddenly near the bank of the Chicago 

 river. It does not reappear on tlie opposite side of the river. The interval 

 between the eabtern end of this ridge and the western terminus of the si)ur- 



