THE Geological Survey of Canada, publishes in Memoir 72 an account of “The Artesian Wells of Montreal,” which is suggestive to investigators in other limestone districts. Out of 179 deep wells, only about twenty yield less than 5000 gallons a day. The water usually comes in greatest abundance from depths of 300 to 1000 ft., and rises to within 30 ft. of the surface. The chance of finding a good supply below 1000 ft. is small, and it seems that the source of the water (p. 26) is the rain that falls on the St. Lawrence highlands and lowlands and creeps into the Palaeozoic sediments. This water moves in the limestone along fissures and cracks, and is held up at no particular horizon; the closing of the fissures as the depth increases is held to explain its practical absence below 1000 ft. The author, C. L. Gumming, discusses the origin and possible interactions of the dissolved salts; the proportion of sodium carbonate is high for water in sedimentary deposits (p. 48), and this salt may be deriyed from flow over the crystalline orocks of the Laurentian highlands.