OF DENISON UNIVERSITY. 
123 
ognizable and distinct classes of rock which, in this region at least, 
show no sign of interblending. The first, consisting of slaty rock, 
inclined at a high but varying angle and reposing upon an evidently 
igneous mass of granite which frequently projects through the slates 
where denudation has removed them. The third series occurring only 
as a thin belt for a short distance near cape Cargantua, consists of 
conglomerate and sandstone which laps unconformably upon the slates 
and is largely re-enforced by igneous overflows and intrusive masses 
and forms the entire island of Michipicoten. 
We first directed our attention to the series of slates which varies 
sufficiently lithologically to afford much field for conjecture. First, 
does the cleavage really indicate sedimentation, or is it the result of 
metamorphic action on an igneous rock ? We were fortunate in light- 
ing upon the spot of all others most decisive on this point. It was 
easy to convince ourselves that the cleavage followed closely the sedi- 
mentation planes, for the lithological character of adjacent bands is 
sufifciently distinct to prevent mistake. The occurrence at more or 
less regular intervals of beds of conglomerate altered to schist-con- 
glomerate, was especially decisive. These broad bands containing 
large boulders as well as pebbles of granite and felsite-porphyry, pre- 
serving their water-worn outlines and even jointage planes extend for 
miles along the line of strike. The only stratified granitic rocks seen 
were calcareous gneisses interlaminated with the schists near what is 
assumed as the core of a great fold and thus representing possibly the 
extreme of metamorphism. 
Before proceeding to a discussion of the individual exposures the 
first may be analyzed as follows : I. Greenish, more or less unctuous 
slate varying to mica schist or hornblendic schist, always with more or 
less calcite and chlorite. Although adhering to one facies it is greatly 
influenced by the three classes of intrusives with which it is in various 
places interbedded. 
I. The most distinct of these groups of intrusives is made up of 
diabases and diabase porphyrites which perforate the granite and in- 
tersect the schists in the planes of strike and dip. No difficulty ever 
exists in determining the contacts of these dykes. The aphanitic mar- 
gins nearly always present sharp lines of contact. In some cases (as 
No. 1108) the dyke-rock embraces fragments of granite and wraps it- 
self about the altered fragments. 
