. Geological report on Monroe County, Michigan. them due south. The effect of theice upon the limestone where chert nodules protude is to produce theknob and trail phenomenon. The hard rock protects a ridge oflimestone upon the lee side, while that in front of the nodule andalong the sides is planed off and, in certain cases, grooved. This isconvincing evidence of the direction of the ice movement, and asobserved upon this island and at Monclova, proved that the move-ment was westward, rather than eastward. Upon South Bass Islandthe striae run S. 80° W., with a second series S. 15° W. At San-d
. Geological report on Monroe County, Michigan. them due south. The effect of theice upon the limestone where chert nodules protude is to produce theknob and trail phenomenon. The hard rock protects a ridge oflimestone upon the lee side, while that in front of the nodule andalong the sides is planed off and, in certain cases, grooved. This isconvincing evidence of the direction of the ice movement, and asobserved upon this island and at Monclova, proved that the move-ment was westward, rather than eastward. Upon South Bass Islandthe striae run S. 80° W., with a second series S. 15° W. At San-dusky the direction is S. 80° W., at Ballville S. 65° W., and atGenoa S. 65° W. Vol. VI of the same Survey, in 1888 (page 754),devotes a paragraph to the glacial markings of Kelleys Island andthe local deflection of the ice by prominent joints. The general di-rection of the strife is given as S. 23° W., which striae upon the *2d Annual Report of the State Geologist, p. 113. tReport of 1860. p. 127. ^Ohio Geol. Vol. I, 1873. p. THE GLACIAL EPOCH IN SOUTHEASTERN MICHIGAN. 12{> eastern end of the isJand are found to be crossed by a later set ex-tending S.,76° to 80° W. In Wayne county, to tlie north of Monroe, an examination wasmade of the glacial strife about the Sibley quarry. At the time ofthe first examination a few were found bearing S. 64° W. and theseseemed to be the oldest. A recent inspection of the rock now strippedfailed to show any of this series. Upon three sides of the quarry,and particularly the eastern, the rocks were heavily grooved by anice sheet which moved about S. 28° W. Some of these grooves arefrom one to two feet deep, but mostly only a few inches. It is onlyin these grooves that these strite are preserved. Outside they havebeen replaced by a newer set, the mean of 21 observations giving abearing of N. 27° W. and a range of from N. 19° to 38° W. Theevidence that the sheet moved northwestward, instead of southeast-ward as has been
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