114 Wisconsi7i Academy of Sciences, Arts, and Letters. 



together with great thicknesses of sandstone (Ill.d.) and shale. 

 These sandstone, shale and conglomerate beds do not altogether 

 overlie the trappean beds, hut are, near the junction, directly and 

 unmistaheally inter stratified with them. The whole series, traps, 

 conglomerates, shales and sandstones, have a very high dip to 

 the north, seldom less than 85 degrees, the beds having often 

 a true vertical position. The sandstone, conglomerates and 

 shales have not as yet been seen west of Bad river, in the cen- 

 tral part of Ashland county, but the trappean members can be 

 traced uninterruptedly as far west as Long Lake. 



The outcrops of traps and southward dipping sandstones 

 (IlI.e), already alluded to, I have regarded as being really the 

 same as those just described, forming the opposite edge of a 

 synclinal.* These rocks are exposed only in isolated patches, 

 those thus far seen in Ashland county, being sandstones only, 

 of great thickness; but on the same line further west, in Bay- 

 field county, trap occurs. 



tSilurian. — Over all that portion of Ashland county north 

 of division " B '' of the copper bearing series, there is an 

 immensely thick mass of a peculiar red marly clay, almost 

 every where concealing the underlying recks, which are 

 exposed in but very few places. In the interval between 

 " B " and the line of southward dipping sandstones, are found 

 horizontal sandstones and shales in every way similar to 

 those on the Apostle Islands, which last constitute the fourth 

 great group of northern Wisconsin. These sandstones are, 

 without doubt either the exact equivalents — or, which is 

 more probable the downward continuation — of the light- 

 colored primordial sandstones of the Mississippi valley. They 

 form every where the basement rock of the Apostle Islands, 

 and of the adjoining coast of Bayfield county. Following 

 them westward into Douglas county they can be traced, with 

 the same horizontality, to exact junction with the copper 

 bearing traps of that part of the state, (Ill.f.) Farther south> 



*See section. 



