Of Maimanse, L. Superior. 3 



ance, but not calcareous and j^ossibly a mixture of sand and 

 volcanic asL ; conglomerate with syenitic pebbles ; laminated tu- 

 faceous beds, made up of yolcanic ashes , and scoriae ; and beds 

 of amygdaloidal trap. They dip at high angles to the south- 

 ward, but very irregularly ; the dips observed along a small extent 

 of shore varying from S 10° E to S '70° W. At one part, they 

 are traversed by a thict dyke of trap, in contact with which 

 tlie sandstones are changed into coarse banded jasper. 



An observer approaching these rocks from the eastward, must 

 at first sight, form the opinion that he has reached a lower mem- 

 ber of the red sandstone series of the lake, modified by the prox- 

 imity of rocky coasts and contemporaneous and subsequent ig- 

 neous action. A geologist familiar with the red sandstones of 

 other regions and periods, would be the more inclined to adopt 

 this view, from the circumstance, that the coating of white sand 

 with peroxide of iron to form red sandstones, has usually, if not 

 always, been a secondary consequence of volcanic action ; and 

 hence, the association of red sandstone with trap and tufa is very 

 frequent. For this reason, the appearance of the red rocks of 

 Sault St. Marie would alone be sufficient to prompt the question — 

 are there, in the continuation of these beds, any evidences of 

 contemporaneous volcanic action ? 



On the other hand, the high inclination and disturbed condition 

 of these rocks, render it not imj)robable that, as Sir W. E. Logan 

 has shown to be the case with the somewhat similar rocks on the 

 north side of Lake Huron, they uncomformably underlie the 

 Potsdam sandstone, which in that case may be in part made up 

 from their waste. 



The promontory of Maimanse is high and rugged in its interior, 

 and in approaching from the east, its outline presents a series of 

 abrupt protuberances. This appearance is caused by the out- 

 cropping edges of thick beds of trap and conglomerate, which 

 have, better than the associated tufa and sandstone, resisted the'' 

 denuding agencies, which in this region appear to have most tho- 

 roughlj' swept all the elevated tracts, scooping out the soft 

 beds and carrying ofi" all the finer materials, as if the forces of 

 breakers and strong currents had been combined in the operation, 

 along with the drifting agency of ice. 



In a point at the west side of Anse aux Crepes, the beds of 

 sandstone and trap are seen in a less disturbed state than in the 

 bay itself. Two very thick beds of amygdaloidal trap are here 



