OF DENISON UNIVERSITY. 
125 
Description of the Rocks of Michipicoten Bay. 
It has been thought best to present these descriptions in about the 
order in which they were examined by us, in order to place the reader 
as nearly as possible at the same standpoint in regard to the questions 
under discussion. 
At the mouth of Dog river and extending along the coast for some 
miles is No. 1001. Typical chloritic slate, strike S. 32° E., dip 80° N. 
E. Very fissile and somewhat unctuous. Under the microscope, the 
magma is close-grained, with much chlorite, irregular scales of biotite, 
large irregular grains of calcite, occasional fragments of orthoclase, 
fewer quartz grains, numerous crystalline grains of magnetite, and 
some irridescent white scales which may be talc. The calcite, which is 
characteristic of most of these schists, is here frequently granularly 
decomposed in the centre of the grain. It is easily recognized 
even in small grains by its irridescence and in larger ones by the rhom- 
bohedral cleavage and twins. 
Nos. 1005-1007. Same slate as No. 1001, but modified by con- 
tact with dyke of No. 1004. The surfaces of the lamellae are covered 
with wavy ridges arranged in ‘^cohesion figures.” The dark ingredi- 
ents are collected in zones of varying width. Grains of orthoclase 
and plagioclase* occur as well as quartz, which last in some cases is sur- 
rounded by a zone of radially arranged fibres or plates of chlorite. 
The calcite is also collected into zones. In one place (No. 1007) in 
proximity to a quartz vein the rock is largely made up of rather regu- 
lar though decomposing feldspar, chiefly orthoclase in Carlsbad twins. 
The contact with the quartz is sharp, but the latter is permeated at the 
edges by calcite and into it are fused iron globules from the schist. 
Both these circumstances give evidence of high temperature during 
the formation of the vein. 
At the point one half mile east of Dog river is a wide band of 
conglomerate (No. 1023 see beyond) passing which, we encounter 
broad bands of yellowish felsite-porphyry and obliquely arranged len- 
ticular masses and strings of a similar character (Fig. 5, Plate XL ) 
No. 1008 is a specimen from the lenticular masses and consists of 
an exceedingly fine-grained felsitic magma, containing large rounded 
grains or nearly perfect crystals of quartz and feldspar, (Plate XI, Fig. 2.) 
The grains of quartz, though greatly rounded, appear to have been 
doubly terminated crystals, while the feldspar, which is nearly all or- 
