Mesozoic and Caenozoic Geology and Paloeontology. 301 



beach, 12 feet ; 1st drift terrace, 29 feet; 2d drift terrace, 46 feet; 

 3d drift terrace, 75 feet ; summit of plateau, 94 feet. 



The rocks in many places are grooved, scratched and polished. 

 These phenomena, of course, can be seen only where the drift deposits 

 are absent. The groovings consist generally of parallel furrows, from 

 one to four lines wide — sometimes extending a foot, at others many 

 yards. Where the rock is very hard, they are mere striae. Hollow 

 spots occur, as if they had been scooped out by a round instrument? 

 and also wide bowl-shaped depressions, known as troughs, which have 

 been caused by the same agency. Grooves and scratches were ob- 

 served on the road from Eagle river to the Clifl' mines running N. 15° 

 E. On an island east of Dead river there are two systems of strife — 

 one running N. and S., and the other N. 20° E. and S. 20° W. The 

 rock here which is very hard and tough hornblende, is not only grooved 

 and furrowed over its whole extent, but there are, beside, deep trough- 

 like depressions, with perfectly smoothed walls, some ] 2 to 15 feet long, 

 4 feet wide, and 2^ feet deep. On Middle Island, east of Granite 

 point, troughs may also be seen 4 feet wide, and 2 feet deep, running 

 like the strise N. 20*^ E. On the promontories and islands near Wor- 

 cester, two miles west of the mouth of Carp river, there are two distinct 

 sets of striifi ; those running N. 55° E. are the most numerous ; those 

 running N. 5° E. the least. The latter cross the former and are there - 

 fore more recent. Some of them are, beside, distinctly curved, as if 

 the body which produced them had been deflected in ascending the 

 slope. Each set of stritB extends only about one foot below the water's 

 edge. On the first quartz ridge, one mile from the mouth of Carp 

 river 500 feet high, the strits run N. 20° E. On the iron ridge south 

 of Teal lake, 750 feet high, the strise run N. 55° E. At the Jackson 

 forge N. 05° E. A green magnesian rock, with vertical walls, and semi- 

 cylindrical form, on the road leading from Jackson landing to Teal lake 

 is covered with striae which may be traced along the surface, like hoops 

 around a gigantic cask. On Isle Royal the striai run N. 50° E. with 

 many local deviations. On the shores of Ackley bay striae near the 

 water's edge running E. and W., cross others running N. E. and S. W., 

 and others again running S. 75° E. Isle Royale presents but little 

 evidence of drift, though scattered bowlders are found upon it; the 

 surface of the rock s are generally, however, smoothed, as if polished 

 off. 



Mr. E. Desor described the superficial deposits on the northern 

 shore of Lake Michigan, the western shore of Green bay, the Big Bay 



