Age of the Quartzites^ Schists^ Etc.^ of Sauh Co. 133 



many places, are thin layers of a schist principally siliceous, 

 but having always some talcose material. These correspond 

 apparently to the clayey or shaly layers between the beds of 

 sand now represented by the quartzite. In some places these 

 layers seem to be merely a thinly laminated qu.artzite, with 

 talcose films covering the laminae ; in others, the talcose mate- 

 rial pervades and gives character to the whole mass, the sili- 

 ceous material, however, always being present. 



The most remarkable feature of this locality is, however, the 

 very striking system of vertical joints which everywhere inter- 

 sect the quartzite. The bearings of these joints, taken in some 

 fifty or sixty different localities, I found to be unifonnly KB. 

 and S.W. and S.E. and N.W., the variations in a few places 

 being evidently due to local displacement. On the cliff sides, 

 and more especially about the lake, these joints, together with 

 the bedding joints, have so cut the rock into separate blocks, 

 that these have from time to time been thrown down the bluff 

 by frost and atmospheric agencies in huge rectangular masses, 

 weighing by calculation from seventy -five to two hundred tons 

 apiece. 



In many places along the north flank of thi^ ridge and lying 

 always above the quartzite, are outcrops of a conglomerate, 

 containing pebbles unmistakably from the quartzite below, 

 always rounded, and in size varying from a few lines to four or 

 five inches in diameter. In some few places there seems to be 

 a second conglomerate in which the sandy cement itself appears 

 altered to a quartzite. This is a point, however, deserving of 

 further investigation. There are also places where distinct 

 layers of coarse and fine conglomerate occur, the latter always 

 above and gi-aduating into a simple sandstone. 



In this conglomerate are found in one locality just northeast 

 of the lake, the Potsdam fossils described by Mr. Winchell in 

 the article referred to, viz. : ScoUthus linearis Hall, Orihis Bara- 

 huensis Hall, Delphinocephalus Minnesotensis Owen, etc. I have 

 examined a collection of these fossils from the above locality, 



