The performance of a thermal ice-drill having a smooth, solid, impervious frontal surface, termed a “solid-nose hotpoint”, is determined by the velocities, pressures, and temperatures in the thin layer of warm melt water between the hotpoint and the ice. The efficiency, the speed of penetration, the temperature of the frontal surface, and the distribution of pressure on it can be calculated from the equations of non-turbulent fluid flow. For hotpoints whose frontal surfaces are isothermal and axially symmetric, these quantities are functions of the total input of power Q of the weight W on the hotpoint, of the radius a and “shape factor” S of the frontal surface, and of the pertinent physical properties of water and ice. The calculation shows that with increasing “performance number” the efficiency E decreases and the surface temperature θ0 increases. Thus, for example, E = 1·00 and θ0 = 0°C. when N = 0.0 E = 0·76 and θ0 = 48°C when N = 1.4; and E = 0·60 and θ0 = 103°C. when N = 3.0. The coefficient Λ is a constant equal to . The shape factor S is a dimensionless number between 0 and 1 that varies according to the shape of the frontal surface, greater values of S being associated with blunter profiles (thus S = 1.0 for a plane frontal surface perpendicular to the axis). For coring hotpoints the same numerical results are obtained, but the performance number is given by

where 2ϖia is the inside diameter of the hotpoint.

An analysis of the iceberg count off Newfoundland for the period 1880–1925 shows that stronger than usual north-westerly winds off the Labrador and Newfoundland coasts and relatively low temperatures over Newfoundland during the months from December to March lead to greater than average berg counts off Newfoundland in the following months, mainly April to June. Conversely, lighter than usual north-westerly winds and relatively high temperatures lead to lower than average berg counts in the following months. The relative strength of winds can be measured by the pressure difference between Belle Isle and Ivigtut. The relationship investigated provides a basis for predicting the berg count each year at the end of March. A comparison of the computed values of the berg count with the actual values on scale 0 to 10 for the following period 1927–61 shows marked agreement.

It is further indicated that a more detailed representation of the winds, temperatures and other elements during the winter and early spring in that general area would lead to a closer relationship with the berg count and a broader basis for its prediction.

The Antarctic Ice Sheet responds quickly to regime changes, and time lags in its fluctuations are relatively small. During the Pleistocene glacial stages of the Northern Hemisphere, world-wide temperature reductions reduced the plasticity of the ice sheet and made it thicker. The amount of thickening depended on the conditions at the ice base but it was small, for mechanical and thermal reasons. Also, during the northern stages, accumulation over Antarctica was probably less than now, but this too had little effect on the thickness of the ice sheet. The mass budget of the ice sheet alone, without the ice shelves, probably remained strongly positive; the ice sheet probably existed throughout the Pleistocene and is unlikely to disappear in the future. The area of the ice sheet is determined chiefly by the elevation of the “grounding line”, where the peripheral ice cliffs and ice shelves begin to float. During the northern stages, world-wide lowerings of sea-level displaced the grounding line downwards and northwards, and allowed the ice sheet to advance by amounts which account for nearly all the evidence for previous greater glaciations. In summary, the glacial history of most ice-free areas is governed not so much by climatic as by sea-level changes. Therefore, Antarctic glacial fluctuations were dependent on and in phase with those of the Northern Hemisphere. The field evidence from Antarctica has little bearing on the ultimate causes of glacial fluctuations, which might however be determined by field work on the planet Mars.

Studies of the geomorphology and rock lichen development north of the Barnes Ice Cap prompt the conclusion that 70 per cent of this extensive, interior region was covered by permanent ice some 300 to 400 yr. ago. Contemporaneously the northern Barnes Ice Cap was significantly larger than today; it dammed up a lake in the upper Isortoq valley, over 80 km. long and up to 300 m. deep. Excluding the ice cap less than 2 per cent of the area is glacierized today; this represents a dramatic reduction in surface area of the former ice cover. Similarly, significant recession of the ice cap implies that glaciers of the “Baffin type” are in a less healthy budgetary state than hitherto has been assumed.

Proof of former extensive ice cover rests largely upon restricted rock lichen development. When sufficient time has elapsed for complete colonization, few indications of the former existence of an ice cover will remain. This type of glacierization may have affected large areas in the high Arctic. Absence of evidence of glaciation, therefore, cannot be relied upon to delimit nunatak areas (plant refugia) during the last glaciation.

Observations were made on the density of naturally and artificially formed lake and river ice. The effect of initial snow density, size and shape of snow crystals, rate of water spread and rate of freezing on the density of snow-ice obtained was studied in the laboratory and is presented in graphical form. The observations indicate that snow-ice formed under natural conditions will probably have a density between 0.85 and 0.90 g./cm.3. The classification of snow-ice is discussed briefly.

The structure of silty ice bands and the formation of their resulting shear moraines are investigated in the light of new evidence provided by two ice tunnels and additional surface investigation in the general Thule area. Previous investigations are examined and discussed; a new interpretation of the phenomena is presented.