The Manitounuck series is largely made up of rocks of volcanic origin and I have obtained specimens of diorites and porphyry from the north-western part of the bay. The probable site of the original source from which these rocks have been derived has not yet been ascertained. A set of immense dykes of trap along the Mattagami River running northward towards James’ Bay, was described in my report for 1875; and other dykes, having the same general course, were found along the east side of James’ Bay in 1877. No irregularity has been found in the bottom of Hudson’s Bay which might indicate a seat of volcanic disturbance in former times. The unexplored district behind Cape Henrietta Maria may yet throw some light on this subject. The volcanic rocks of the Manitounuck group of the Eastmain coast and the islands opposite to it may have been originally derived from the neighbourhood of Clearwater Lake to the eastward of Richmond Gulf. Between Lake Superior and Hudson’s Bay, I have observed that, other things being equal, the water of lakes where igneous rocks prevail, is much clearer than those surrounded by gneiss or schists. The Rev. Mr. Peck visited the lake referred to in 1884, and he informs me that it merits its name from the clearness of its waters. [Sidenote: Schistose bands.] [Sidenote: Labrador Peninsula.] Schistose bands and areas which have been classified as Huronian are largely developed within the general limits of the Laurentian country to the south and west of James’ Bay and apparently also on the north-west side of Hudson’s Bay, but to the eastward few indications of these rocks have yet been discovered. The Labrador peninsula measures, as nearly as possible, 1,000 miles from the Straits of Belle Isle due west to the Eastmain coast of James’ Bay, by 1,000 miles from Cape Wolstenholme, on Hudson’s Straits, to Mingan on the Gulf of St. Lawrence. The interior of this vast region has not yet been explored geologically, except to a very limited extent, so that rocks of the class called Huronian may exist in great force in some parts of it. A non-fossiliferous, but unaltered limestone, like those of the Manitounuck group is found around Lake Mistassini near the head of the Rupert River in the southern part of the above region. [Sidenote: Rocks of Baffin Land.]