The heat exchange takes place in two stages: (i) the atmospheric heat causes melting of the whole of the annual snow accumulation and leads to the formation of slush rivers; (ii) some of the melt water refreezes to form a new layer of ice superimposed on the original ice, which is warmed by the latent heat yielded to it. A theoretical estimate of the rate of formation of the superimposed ice, and of the temperature change in the original ice, is given, which agrees reasonably with the actual measurements. A rough measurement of the melt water run-off checks with the observations of ablation and superimposed ice. The total energy available for melting is estimated approximately from the meteorological observations; it underestimates the actual ablation. About 70 per cent of the total ablation energy (47 cm. water, total ablation) is disposed of as melt water that is discharged from the ice cap surface; the remainder goes as sensible heat to the low temperature ice.

Contrary to prevailing opinions, the glaciers of south Patagonia have normally been stationary or have advanced during the last twenty years. Exceptions can be accounted for by a lag due to a long travel through narrow passes or by the lowering of waters in the terminal lake at the foot of a rocky cliff.

Snow crystals were received on the collodion film of the holder of an electron microscope, and made to sublimate without melting. These specimens were investigated under an electron microscope. One solid nucleus was always observed in the central portion of a snow crystal. These centre nuclei were of sizes between 0.5 and 8μ. Most of them were presumed to be kaolin, clay or carbon particles; some were considered to be micro-organisms. In the other parts of snow crystals numerous smaller nuclei were observed, whose dimensions were of the order of those of condensation nuclei. These condensation nuclei were found to be of two kinds, the larger ones most frequently having a diameter of about 0.15μ, the smaller ones of about 0.05μ. A new theory was proposed from the data of the electron microscopic studies and those of the conditions of formation of snow crystals. In this theory it is proposed that minute water droplets of 1μ or so play an important rôls in the process of snow crystal growth.

A summary of the winter conditions at the edge of the pack ice around Antarctica, as observed on 16 occasions by the R.R.S. Discovery II between 1932 and 1951, is followed by a more detailed account of each visit. The state of the ice on the northern fringe of the pack is noted especially with reference to the various stages in the formation of pack ice. Detailed reference is also made on each occasion to the meteorological conditions obtaining not only during the ship’s stay on the ice edge but for 2 or 3 days beforehand. Despite the limited number of observations possible it would appear that the state or condition of the ice edge, at any one point in winter, is Iargely dependent on local weather conditions, and it is suggested that, basically, the condition of the ice edge falls into three or, possibly four main categories.

Attention is drawn to the possible relationship between the sea surface temperature and the condition of the ice on the fringe of the pack but it is considered probable that the surface temperature has a greater effect on the distribution of pack ice generally, rather than on the state of the ice edge locally.

The ground in Spitsbergen is frozen to a depth of about 320 m., as can be seen from observations in the collieries. At a mean surface temperature of −8° C. this corresponds to a geothermal gradient of 1°/40 m. The temperature of the sea water is almost 0° C. Along the coast the land lies very little above the sea level, and here the sea is shallow. One assumes that the land as well as the sea bed is horizontal. Thus the temperature on the land is –8° C., in the sea 0° C. On the coast the temperature must suddenly change. One must also take into account the fact that the temperature rises with depth. A simple calculation leads to the conclusion that the frozen ground below the sea bed must extend about 100 m. from the coast. Investigations near a Swedish colliery have shown this to be the case.

This result also applies to the conditions underneath a glacier. On the same assumptions one can conclude that if the glacier is less than 400 m. wide the frozen ground underneath forms one coherent layer and that this is not the case if the glacier is wider. The same applies to a shallow fjord.

A method of quantitative climatological analysis is developed by applying the principle of geometric similarity to the convective heat transport, which is assumed to vary with the 1.5 power of temperature difference. The method makes possible the calculation of the change in the mean annual, or seasonal temperature, produced by a variation in insolation, cloudiness, snow cover, etc.

It is shown that the variations in the orbital elements of the earth cannot account for the phenomena of the ice ages; the chronology of the Quaternary, based on these variations, has no real foundation.

Palaeoclimatic variations are most probably due to variations of solar luminosity. These can be traced to periodical re-adjustments in the interior of the sun, produced by an interplay between nuclear reactions and gas diffusion, repeating themselves after some 250 million years. Complications from the outer envelope of the sun lead to additional fluctuations of a shorter period, of the order of 100,000 years to be identified with the periodical advance and retreat of the glaciers during the Quaternary.

Calculations of the variations of luminosity in a star of solar mass substantiate this hypothesis.