A SERIES of valuable tables and charts, in which the results of a great series of observations made in 1901 by Captain Roald Amundsen in the Arctic Seas are summarised, is contained in a monograph recently published.1 These observations are supplemented by, and compared with, results published by other observers, chiefly Russian and Norwegian, and as a collection of facts the little volume is certain to prove of great value to all students of oceanography. Dr. Nansen?s. main purpose in the discussion of the observations has been the scientific explanation of the origin of the intensely cold and heavy?bottom waters? found in the basins of the Norwegian seas and North Polar Ocean. In discussing the scientific results of the Norwegian North Polar Expedition of 1893?6, Nansen had already dealt with this subject, and reached the provisional conclusion?that the cold bottom water of the Barents Sea is divided into two portions; the northern cold water coming from the sea to the North, North East, and East; and the southern cold water having two or three sources, namely bottom currents from the East and North East, and the surface of the sea itself which is cooled during the winter.? In the light of more recent and extensive observations, Nansen has revised his opinion, and puts forward a different explanation of the origin of bottom water. This explanation accords with the facts observed, and may be briefly summarised.