An examination of rates of ice growth, actual ice thickness and the quality of the lake ice profile on Knob Lake, central Labrador—Ungava, showed that all these factors were extremely variable. Three sites were established on Knob Lake from 1957 to 1961, and a similar sequence of sites was established on a neighbouring lake, Maryjo Lake, from 1959 to 1961. Significant variations occurred within a single lake body from site to site, though it was noted that certain patterns of ice growth and quality did occur throughout most years and could be directly related to patterns of snow accumulation on the lake. Variations from lake to lake were found to be least at the centre lake sites, probably because snow cover was always least at these sites and would not affect heat loss so greatly as at the marginal sites. It is suggested that the majority of empirical formulae proposed for lake ice growth are unrealistic for short-term forecasting of ice thickness and growth, and even long-term forecasting, using accumulated degree-days of frost, only gives average values. The only answer is repeated samplings on any lake, until such time that sufficient data are gathered for a full statistical approach based on probability analysis.

The occurrence of ice mounds, which were observed in the western part of the Sør-Rondane by a geological and gravity reconnaissance party of the 1960 Expédition Antarctique Belge, is described. An explanation of the origin of these mounds could be the refreezing of an accumulated pocket of melt water within the ice. The possibility of the formation of pockets of melt water, despite the severity of the climate, is discussed in relation to several examples of the melting of snow and ice. It seems that such a pocket could form above the higher mounds of the underlying moraine by the hot-house effect.

A new advance since about 1954 of the glaciers descending on all sides of the great volcanic mountain Beerenberg (2,277 m.) on the island of Jan Mayen (lat. 71° N., long. 8° W.) has been reported. Annual precipitation in the area appears to have risen fairly steadily and in the 1950’s had almost doubled as compared with the 1920’s. Other places around the Greenland Sea show substantial increases of precipitation after 1920 as compared with the 1910–20 rate, but mostly attained a maximum in the 1930’s or around 1940. Periodicities are briefly discussed as well as secular change. Temperatures at Jan Mayen have fallen somewhat since the 1930’s but they have not altered much since the 1940’s. The likely causes in terms of changes of the atmospheric circulation and other circumstances, including lag in the glaciers’ response, are briefly discussed. The increase of precipitation seems to be the main, almost the sole, causative factor in the glacial advance.

Laboratory experiments and field observations permit an explanation of the varying crystallographic orientations observed in lake ice in terms of four factors: (1) coincidence of the plane of most rapid growth in ice (the basal plane) with the vector of thermal flux, (2) mechanical fragmentation of early-formed dendrites and plates by winds above a critical velocity (approximately 2.7 m./sec.), (3) the presence of a sufficiently thick layer of supercooled water to permit vertical crystal growth, and (4) the operation of geometric factors, first pointed out by Perey and Pounder, which result in the gradual elimination of the flatter plates of growing ice by the steeper ones.