The 300 foot hill south-west of Mosher lake is composed of a fine Keewatin greenstone whose surface is curiously weathered so as to suggest a spheroidal structure. It is marked off into round areas a foot or more in diameter by a sinuous network of weathered-out grooves. The main body of the rock is ordinary fine-grained greenstone, but the enclosing grooves have been formed in porphyritic zones about an inch in width. Among other types of less abundant distribution is an actinolite rock seen by the unassisted eye to consist of a felty mass of acicular crystals of actinolite, sometimes half an inch long. This rock was observed 12 chains east of the islanded part of Pigeon lake; also at points west of Montreal river below Pigeon lake. _Unfinished Areas._ The Keewatin formation occupies the space between Near lake and the West branch, only part of which has been mapped. The rocks of this area are well foliated, standing as usual, vertically, and striking about N. 60° E. The exposures on the east shore of Near lake are entirely of fissile, chlorite schist, abundantly traversed by small barren quartz veins. Farther east the chlorite schist gives place to glistening, stratiform (laminated) hornblende gneiss with which are associated bands of a coarser hornblende gneiss, evidently the equivalent of granite. In one locality the stratiform rock contains subangular fragments of the coarser variety, quartz and a greyish eruptive rock, the resultant structure resembling that of a metamorphosed conglomerate or breccia. As some of the brecciated fragments occur near by in continuous bands within the stratiform gneiss, the clastic structure is to be ascribed to deformative movement instead of original sedimentation. A number of fine-grained quartz diabase dikes occur in the immediate vicinity. A considerable portion of the east shore of Kenisheong lake consists of high, bare Keewatin hills, composed largely of chloritic schists, vertically inclined and striking east and west. Secondary calcite is richly disseminated, causing free effervescence when the rock is treated with acid. Pyrite is also abundant, sometimes segregated to form a lean ore, and at several points weathered superficially to limonite, colouring the cliffs dull red. Much-altered diabase like that on Pigeon lake is also present in subordinate amount. [Illustration: Fig. 5. West Branch Montreal River, near Mosher Lake.] Keewatin rocks also occur just east of Gowganda lake. A single brief visit was paid for the purpose of observing the iron formation which appears at this place, and further mention of which is made on a subsequent page. LAURENTIAN. _General Features._