resulted from the decomposition and shearing of granite porphyry dikes probably connected with the Laurentian, and which penetrated the Keewatin during the time of Laurentian intrusion. Serpentine was observed between Foot lake and Obushkong at 20 chains from the latter. The surface is covered by a loose network of fine seams of asbestos which weather white and render the rock somewhat conspicuous. Its recognition is further simplified by the dull green, amorphous appearance of fresh surfaces, the slight translucence of thin edges and the glistening green seams of asbestos which traverse it abundantly. The same rock is more extensively exposed on the south-west of Serpentine lake and on Firth lake half a mile north of the portage leading to the former, also at less than a quarter of a mile south of this portage. It is associated with and derived from a dark green massive rock to which the name wehrlite is applicable, and a more detailed description of which appears later. _Duncan Lake Area._ A Keewatin area of considerable extent lies between Duncan lake and the West branch in the vicinity of L’Africain and Beaverhouse lakes. Unlike the Obushkong area, the prevalent strike of the schists is nearly north and south, the greatest divergence noted being 25° W. In the former case Laurentian lies to the north, while in the present one it occurs on the east; in both cases the schistosity coincides approximately with the direction of the line of contact. On account of the swampy character of the country just west of the river and the scarcity of outcrops, this area was not completely explored, but wherever examined the Keewatin, as in the Obushkong area, consists predominantly of hornblende and chlorite schists, greenstone and decomposed diabase; but serpentine was not found. A nearly black diabase containing small grains of pyrite was observed 20 chains south-east of the southerly extending bay on Duncan lake, and outcrops of the same material were traced for about half a mile northward. Probably the same type was encountered just north of Beaverhouse lake and at some other points. Its unfoliated condition and fresher appearance than the adjacent rocks lead to the opinion that it is really post-Keewatin and intrusive, but the absence of younger rocks with which to correlate it, renders its exact age indeterminable. This rock exhibits enough resemblance to fractured contact edges of the post-Huronian diabase to make their distinction in the field rather difficult. At half a mile east of the south end of L’Africain lake is diabase which from lack of sufficient data has been mapped as Keewatin, although it may be identical with the post-Huronian variety. L’Africain lake lies in glistening hornblende gneiss with which are associated ribbons of a coarser hornblende gneiss belonging to the Laurentian of the area farther east. Greenstone and chlorite schists are the principal rocks around Beaverhouse lake.