ANNUAL REPORT FOR 1878. 15 



out of the rock wliicli we found is at the Oconto Falls, in section 25, 

 town 28, range !19 east, where the Magnesian limestone makes its 

 appearance in the banks of the river and adjacent bluffs. The per- 

 pendicular fall here is about twenty-two feet, and the rapids which 

 succeed make the whole fall of the river about sixty feet. 



" "We first discovered the Potsdam sandstone in section 34, town 



31, range 19, where the bed and banks of a small creek are of this 

 formation. It is a dark-colored loose stone, too soft to serve any use- 

 ful purpose. At the falls of the Peshtigo river, in section 24, town 



32, range 19, this sandstone is of a firmer and finer texture, and may 

 be found useful as a building material. It has also a sharp grit, and 

 close grain, that renders it serviceable for grindstones, and I was told 

 that at an early day it was used for sharpening edged tools. 



" In section 36, town 33, range 19, granite first shows itself, and 

 with other metamorphic rocks, crops out from time to time until we 

 reach the Menomonee river. It is a very abundant material at Pike 

 river, in sections 15 and 16, town 35, range 20, and forms the bed 

 and banks of the river at the falls. In section 34, town 37, range 

 20, trap rocks' are found interspersed with the granite, along the 

 banks of the Peminee-Bon-Won, but after leaving that stream until 

 we reach the north branch in section 3 of the same township, no rocks 

 appear on the surface except granite. At the crossing of the North 

 Branch, trap rocks again make their appearance and are frequently 

 seen in alternation with the granite, until we reach the crossing of the 

 Menomonee river on section 7, town 38, range 20, at the head of the 

 Big Quinnesec Falls; at which point the rocks are mostly granite, but 

 a small area at the top is composed of trap mingled with some talcose 

 rocks. 



"The granite of this region is mostly schistose in character and is 

 frequently coarse and soft, so as to be of little use as a building ma- 

 terial. It often abounds in seams, filled with feldspar, and other sub- 

 stances; and quite frequently these seams cross each other at acute 

 angles. 



" From the Peshtigo river I went westward as far as Thunder "Lake, 

 in section 15, town 32, range 18, and first discovered the granite in 

 this direction near the line between ranges 18 and 19, and at the 

 point between sections 13 and 18. 



"At Keshena in town 27, range 15, or a little northwest from the 

 village, the same rocks appear; and I judge that the line between the 

 sandstone and granite follows about a northeasterly course to the Me- 

 nomonee river, in town 36, range 21 east." 



'These and the following rocks spoken of as trappean are metamorphic 



