230 On the Geography and Geology 



visible near Michiliraackinac in Lake Huron, although only in 

 numerous angular .fragments ; it overlies transition rocks in that 

 lake, at La Cloche, 120 miles east from the Falls of St. Mary, and 

 is, probably, contemporaneous with the sandstone of Niagara and 

 Genesee. It is composed chiefly of grains of quartz, white or 

 coloured, usually fine ; small fragments of flesh-red feldspar are 

 often present and sometimes abundant ; and a few spangles of 

 mica. It is without cement, or there is a sparing quantity of 

 argillaceous or ferruginous matter. Mr. Schoolcraft reports two 

 examples on the south shore, of the presence of lime ; the sand- 

 stone of the Mammelles and Nipigon Bay often effervesce also on 

 application of acids. It does not cohere very strongly, but in 

 many cases, as at the rapids of the Nibish (Lake George), it is 

 very hard, and imperfectly crystalline. Commonly it is divided 

 into thin layers ; but on the east shore of Batchewine Bay it is in 

 masses five feet thick. Its colours are red, brown, white, and 

 yellow, single tints prevailing throughout a precipice, or alternating 

 in layers, or again, several staining the same layer in clouds, spots, 

 and rings. Solitary colours, as brown and white, are common in 

 the north, while the variegated form is most abundant in Batche- 

 wine and the River St. Mary. 



I was so fortunate as to be twice ashore at the junction of this 

 sandstone with the amygdaloid of the Marmoaze, which is exposed 

 to view at the west angle of the Bay south-east of that point. It 

 is here greatly altered in constituents and in position. It is a 

 particoloured work, massive and schistose in portions, soft, coarse 

 granular, and likewise, in patches, consisting of large fragments 

 of its own substance. It is non-cff'ervescent in acids, except where 

 calcspar happens to be present, which it now and then contains, 

 together with numerous spots and masses of green earth, some- 

 times so plentiful as to colour the rock. It suffers much from 

 weather. When slaty it is red, yellow, and white, in layers ; 

 when massive its colours are in clouds, green then being often 

 prevalent. This rock is highly inclined in various ways. At the 

 east end of the Cape*, it runs .conformably to the trap adjacent, 



* These Capes are never literal points 



