THE LOWER SILURIAN ROCKS. 531 



westward from Grraud Rapids as far as Merrillon, Sec. 15, T. 23, R. 4 

 "W., Jackson county, thin, shaly sandstone is frequently exposed in 

 low cuts, but having evidently a small thickness only, for, at the cross- 

 ing of Black river, gneiss is exposed, as also on Yellow river, a short 

 distance north of the railroad crossing. Between Grand Rapids and 

 Dextervillo, the sandstone does not stretch far north of the railroad 

 line, for along the wagon road between the two places granite is seen 

 at the surface. 



On Yellow river the crystalline rocks are first exposed about two 

 miles above the railroad crossing, beyond which point they are con- 

 stantly exposed in the bed of the river, sandstone appearing at points 

 on the west bank as far north as the northern side of town 24. Rocky 

 Run, in towns 23 and 24, is on crystalline rocks. In the towns on 

 the divide between Yellow and Black rivers, sandstone appears to be 

 generally the surface rock, the Archsean only occasionally appearing 

 through it. All along the road from the crossing of Yellow river, on 

 the south line of T. 25, R. 2 E., Wood county, "to Neillsville, in Sec. 

 14, T. 24, R. 2 "W"., Clark county, the country is generally high and 

 heavily drift-covered, wells passing through 5 to 100 feet of drift 

 into sandstone. Sandstone is also occasionally seen at the surface, as 

 in the road on the S. E. qr. of Sec. 12, T. 24, R. 1 W., and in an out- 

 lying bluff at the center of the S. E. qr. of Sec. 12, T. 24, R. 1 E. 

 Sandstone also occurs in angular fragments on the ridges along the 

 west fork of Yellow river in T. 25, ranges 1 and 2 E. Further north, 

 in towns 25 and 26, ranges 1 E. and 1 "W., drift covers the rocks 

 heavily, and the exact extent of' the sandstone has not been ascer- 

 tained, as indicated by the blank space left on the map. O'Neil's 

 creek, in T. 24, ranges 1 and 2 W., cuts down to the older rocks. On 

 Sec. 11, T. 24, R. 2 W., sandstone occurs by the side of the road, and 

 again in a high outlier on Sec. 3, of the same town, on the west side 

 of Black river. Westward from this outlier the country shows sand- 

 stone at the surface. Similar bluffs occur in T. 25, R. 2 W., the crys- 

 talline rocks showing along the river, and at least one such bluff oc- 

 curs in T. 26, R. 2 W., its exact location not being known to tlie 

 writer. In T. 26, ranges 3 and 4 W., sandstone is reported by Dr. 

 Randall 1 as extending as far as the Eau Claire river, beyond which it 

 is absent. At the crossing of Black river, one mile west from Neills- 

 ville, S. W. qr. of Sec. 15, T. 24, R. 2 W., granite is exposed in the 

 river, and is overlaid by sandstone in the banks. Similar conditions 

 hold 'all along the river, as far as the falls in T. 21, R. 4 W., the 



1 Owen's Geological Survey of Wisconsin, Iowa and Minnesota. 



