In the Keewatin area between Firth and Obushkong lakes there occur masses of a basic igneous rock through whose decomposition serpentine and asbestos have been developed. The localities given in connexion with the description of the Keewatin may be briefly restated. Two bodies were found. One of these, lying east of Foot lake and 20 chains from Obushkong was traced for a width of 4 chains, but nothing learned of its north and south extent. It consists very largely of green serpentine traversed by a network of fine, white weathering veins of asbestos. More extensive outcrops exist along the east shore of Firth lake. At somewhat more than a mile from the foot of the lake and near a small log shack at the water’s edge a considerable mass of partially decomposed wehrlite, serpentine, and asbestos is visible. The main mass is of dark green colour, the asbestos traversing it abundantly as a series of glistening bright green threads. The seams are small, none being found more than 1/4ʺ in width, but the asbestos fibres are fine and elastic. The serpentine is often coarsely fibrous but brittle. ORIGIN. Microscopic examination shows the serpentine and asbestos to be the product of decomposition of the wehrlite, a nearly black medium grained igneous type. Alteration has obscured its original character, but sufficient of the primary constituents remain to admit of its determination. It consisted of olivine, diallage, and common hornblende, with considerable ilmenite and apatite, but plagioclase is apparently absent. Hornblende and diallage form the basis of the section in which lie abundant rounded or idiomorphic grains of olivine. The latter is completely altered to a matted intergrowth of fibrous serpentine containing scattered grains of black iron ore. Diallage persists as colourless bi-refringent remnants enclosed by a felted mass of decomposition products, chiefly long scales of talc. The hornblende is fresher and strongly pleochroic, the tints being green; its alteration begins by bleaching, followed by development of colourless fibres of low bi-refringence, possibly serpentine. Primary ilmenite is replaced by irregular patches of leucoxene, showing gridiron structure. The final product of alteration is a soft green serpentine rock composed almost wholly of that mineral. The limits of these masses are exceedingly difficult to define, owing to the fact that they are associated with other Keewatin rock and basic forms of the post-Huronian diabase, to which it presents considerable resemblance. The asbestos actually seen is probably too short and small in amount to be valuable, but the high commercial value of this material renders delimitation of the wehrlite masses advisable. Asbestos of very good quality has been found by Mr. George Rahn in the vicinity of Sinclair mountain, so that this mineral may be one of the district’s latent resources. CANADA