Relation of the Sandstone^ etc., of the Barahoo Valley. 127 



waves of the Potsdam sea. On the south the action, appears 

 to have been gentler than on the north, for the quartzite has 

 been triturated to a fine sand, containing, to be sure, larger or 

 smaller pieces of quartzite well rounded. The northern shore 

 must have been exposed to the breakers, which washed out 

 the fine sand and left pebbles of a uniform size. It may be 

 that within the circle of these islands was a sheltered bay. 



At the point marked (5) on the map is a limestone quarry. 

 The limestone is horizontally bedded and rests on the southern 

 flank of one of the ridges, but all points of junction with the 

 underlying rock are concealed. About half a mile distant is 

 sandstone on the same level, and in another direction is sand- 

 stone at least 100 feet higher, I am inclined to regard this 

 limestone as a local deposit of the Potsdam epoch rather than 

 of the Lower Magnesian epoch. The latter supposition would 

 require an enormous erosion between the putting down of the 

 Potsdam sandstone and the Lower Magnesian limestone. The 

 fossils, also, a number of which were secured, although unde- 

 termined, have more the aspect of Potsdam fossils than of 

 those of the following epoch. A number of cephalic shields 

 of a trilobite, with other fossils, were obtained. 



Another feature of interest in this region is the evidence of 

 glacial action aside from the dift. At the point (3) on the map 

 is an isolated hill of sandstone. On my visit the earth had 

 just been removed from a large surface in order to quarry the 

 rock. It was entirely smoothed and covered with glacial 

 striae. Their direction is N. 66° E, On the surface of the 

 limestone previously mentioned, the polishing is even more 

 perfect, and the striae have the same direction. Polished sur- 

 faces have also been observed three quarters of the way up the 

 quartzite hills. The most reasonable explanation of the de- 

 flection of the striae from the us^ual direction seems to be, that 

 they were produced by ice masses small enough to be influ- 

 enced in their motion by the east and west trend of the ridges. 



