GEOLOGICAL EXPLOEATIONS AND LITERATURE. 



31 



declivities, at the base of which lies the level country of the Silurian sandstone, in 

 which is cut the basin of the late. From this point eastward this ancient erosion 

 had made great inroads upon the continuity of the Cupriferous and older rocks before 

 the deposition of the Silurian sandstone. The inelaphyre ridges are broken into 

 knobs, or are wanting, and no Hiu'ouiau was found as far as the Ontonagon river, 

 7 miles away, and the limit of our observations. (Pj). 430—131.) 



I8r3. 



Beooks (T. B.). Geological Survey of Alichigau, Upper Peninsula, 1869-1873, 

 vol. I, New York, 1873, with an Atlas. 



Scale J3 miles -J inch . 



Fig. 2. — KepriMlnrtioii nC a portion of Brooks autl Pumin-'lly'a ct'olojcic'il map of 

 the upper peninsula of M ii-hi^'un. 



In Part i of this volume, chapter vi (pp. lS3-lS(;)is eiititlpil "Lake 

 Gog'ebic anil Montreal River Iron Rant;e." This yi\es a lirict' mitline 

 account of the occurrences in the iron belt l)etween Montreal lixcr and 

 Gogebic lake. The account is somewhat fulh-r than that yiven in the 

 paper quoted immediately above, but is based on the same rapid examina- 

 tion, and contains no details. Un the general map of tlie Xortlifrn penin- 

 sula, given in the atlas which accompanies this i-cpoi-t, the Michigan end of 

 the Penokee series is first mapped, Fig. '1 is copied from the western por- 

 tion of this atlas map, 



