N. W. Portion of Lake Huron. 261 
splintery ; so much so that the precipice Saaueny. ere 
into a steep declivity of schistose debris. At ead of 
the narrows the greenstone is much less las wsters and 
dips into the clear and deep waters in compact walls of al- 
most pure hornblende. ‘The contiguous islets (filling up the 
interval of a mile between St Joseph and the aaa 
a similar formation, and are composed of aggregated ridges, 
rising to a-great height, and presenting to the current rapid 
slopes of smooth rocks or perpendicular cliffs.* 
he head of the narrows being the seat of a strong cur- 
rent, is one of the north west limits of Lake Huron, Ad- 
bine of islets, dividing the lower fror the upper basin. fe 
a new order of rocks occurs. 
It is of quartz and is of the transition class, as appears 
from its associations, its inclination and the breccias and 
nodules which it frequently contains. It prevails from owe 
to Lake George, (five and a half miles.) Its direction is 
north west, with a dip either vertical or beens 
but at the islets of Encam pment Douce, at the foot of the 
rapids of the Great Nibish, this is perhaps not quite so evi- 
dent from the inn numerable rents and dislocations, and from 
original displacements. 
On the third large island from the rapid of the basins, 
(above mentioned) a parallel stratum of almost sienitic 
greenstone occurs, “ia the same is seen on the main three’ 
miles north north west. It may be a continuation of te 
* Dir. N. W. jes ciel : 
