210 B. N. A. BOUNDARY COMMISSION. 
and appears to be rather a former lacustrine deposit, than the represen- 
tative of the boulder-clay. It is highly calcareous throughout, but did 
not yield any traces of organic remains even when microscopically 
examined. The sand spit opposite the mouth of Rainy River, called Oak 
Point, or Pointe du Chéne, shows much limestone detritus in the form of 
gravel and sand. A few miles north of Rainy River, near Windy Point, | 
several boulders of limestone occur among others of crystalline rocks. 
They become honeycombed on weathering, in a manner somewhat 
different from any before seen. On the southern shore of Bigsby Island 
many boulders occur. They are mostly of Laurentian rocks, but some 
of the honeycombed limestone appear, and one was observed of a species 
of limestone breccia, with yellowish-white pebbles in a reddish paste. 
Near the northern end of this island, a clay bank about ten feet hi; 
forms the shore for some distance, the clay being hard, w! ere 
unweathered, grey in colour, and having traces of stratification. It 
resembles in constitution the other clays examined, effervescing 
strongly with an acid; and holds small boulders, and gravel, some of 
the latter being of limestone. A single limestone boulder was even as 
far north as the north end of this island. The limestone-breccia boulder 
above described, coincides exactly with a rock which Dr. Bigsby mentions 
as occurring on Rainy River not far from its mouth (§ 47.) 
477. It would thus appear, that a line drawn through Driftwood 
Point and running south-eastward to near the position of Windy Point, 
would have to the south west of it a region of abundant limestone debris ; 
while though a careful examination was made to the north—with the 
exception of two or three boulders near Bigsby Island—not a single frag- 
ment of limestone was found. (See Map Lake of Woods). This line, 
furthermore, runs in a direction almost exactly at right angles to the 
prevalent one of the glaciation. The distribution of the debris taken 
together with the direction of the glacial groovings, and the known courses 
of other erratics, would seem to indicate the existence of a limestone 
flooring to the southern part of the lake, which in this case must have 
overlapped unconformably the older metamorphic strata; but may have 
been in great measure removed, before, and during the glacial period. 
No outlyers of the limestone were however found, and I do not-know of 
any unvisited locality in which such may yet be looked for, with the 
exception of Garden or Cornfield Island, which I was unable to reach, and 
which lies low and flat as seen from a distance. 
478. Two other modes of accounting for the appearance and distri- 

