THE LOWER SILURIAN ROCKS. 



593 



and capable of being split into thin slabs (1292) 10^ feet; unexposed, 10 



feet; brownish, red stained, porous limestone, 2 feet; in all about 45 



IV. Potsdam sandstone: including: greensand layer, 1 foot: unexposed, 20 

 feet; white loose sand with brownish greensand, bearing calcareous bands 

 (1290), in a perpendicular escarpment, 5 feet; slope to foot of bluff covered 

 with sand, 84 feet; in all about 110 



Height of bluff 260 



Altitude of summit 465 



West of the western end of the quartzite ranges. The sandstone lying at high levels 

 about the quartzite, in the eastern part of the town of Westfleld, T. 11, R. 4 E., is, without, 

 doubt, both in and above the horizon of the Lower Magnesian limestone, as indicated 

 by the exposures of that roek to the westward. Half a mile south of the Mendota 

 quarry, on the point of the ridge in the E. hf. of Sec. 10, the road crossing the same 



FIG. 48. 



Jizndffan eZieatpej^ 



MAP AND SECTION SHOWING TUB RELATIVE POSITIONS OP EIKY'S LIMESTONE, AND THE SURROUND- 

 ING ROCK EXPOSURES. 

 Horizontal scale 2 miles to 1 inch. Vertical scale 403 feet to 1 inch. A B C D, line of section. 



ridge eastward is cut into brown, friable sandstone, having the proper position and 

 character for the Madison beds. Continuing eastward, the road rises, the ground be- 

 coming full of the cherts characteristic of the Lower Magnesian, but on the southeast 

 comer of Sec. 10, non-calcareous, indurated sandstone is again in place, at an elevation 

 Wis. SUB. 38 



