The occurrence of isolated ice- or snow-covered summits is reviewed. Their existence appears in the first place to be a function of their breadth in relation to the altitude of the firn line on adjacent glaciers; other factors remain to be discussed. Light may thus be thrown on questions of past glaciation of rounded summits in critical areas, and notably on the amount of precipitation then prevailing.

Planimetry of the 15 maps of scale 1:1,000,000 of the World Aeronautical Chart, U.S.A.F., gives 1.726 × 106 km.2 for the surface area of the Greenland Ice Sheet. The hypsometric curve obtained by measuring the area between contours at 1000-ft. (305 m.) intervals with a planimeter gives 2135 m. for the mean height of the ice sheet. The normal area distribution curve of the ice sheet shows that is certainly in the “Inland Ice” type in Ahlmann’s classification. The mean firn line of the ice sheet is at a height of 1390 m. The discharge from the glaciers in the form of icebergs is estimated to be 215 km.3 of water per year, and the nett balance of the ice cap is negative and about 100 km.3 of water per year.

Using the shadow-photograph method the processes of growth of disc crystals and of ice dendrites formed in water are studied. A mechanism of dendritic crystal growth is suggested.

Glaciological studies during the British Ruwenzori Expedition, 1052, included assessment of the extent of Pleistocene glaciation and detailed study of the late-glacial and post-glacial fluctuations of two of the glaciers originating in the Stanley Plateau. Correlation between photographs taken by earlier expeditions, the stratigraphy of lake site excavations and lichen re-colonization provide a good preliminary basis for assessing the climatic fluctuations. Stratification in existing glaciers appears to link up satisfactorily with meteorological observations to indicate two ablation phases annually.

Information concerning the supply area of Morsárjökull, a small outlet glacier of Vatnajökull, was derived from a firn profile measured in a pit 6 m. deep.

The conspicuous bulge on the medial moraine is, by extrapolation from the annual movement, attributed to a former glacial recession between 1890 and 1900. This bulge is correlated with discontinuous moraines near the head of Skeidarárjökull.

Moraines indicating a former greater extension of the glacier are mentioned and evidence showing the recent rapid retreat and thinning of the glacier is presented.

Observations of fall freeze-up and spring break-up, important to subarctic hydrology and to local economy, were made at the Yukon River town of Beaver, Alaska, September 1949 to June 1950. On October 15, with river temperature at 0° C., the freezing together of floating ice crystals formed thin ice pans that gradually thickened. Falling river level and increasingly heavy ice concentration choked off all but main channels. On 25 October ice jammed downstream and produced a continuous ice cover and a temporary rise of about 1 m. at Beaver. After 26 October the river resumed its drop in level until April. Freeze-up appears governed by local channel, current and weather conditions and lacks systematic progression either upstream or downstream.

Spring thaw beginning in late April thawed snow cover and weakened river ice. In early May the river began to rise slowly, but at an increasing rate, until 13 May when ice was nearly free from shore. On 14 May, after a rise of about 3 m. in 24 hours, the ice broke and moved downstream as the flood crest passed Beaver. Downstream progression of break-up is delayed by local ice jams, the chief cause of disastrous river floods, and is advanced by early break-up of large tributaries.

Measurements of heat balance and ablation on glaciers of the Eastern Alps carried out during a total of 45 days since the summer of 1950 indicate that in flat glaciated areas at approximately 3000 m. above sea level 81 to 84 per cent of the energy causing ablation is supplied by short wave radiation from the sun and sky. Only 16 to 19 per cent come from the air in the form of actual and latent heat. On glacier tongues at altitudes of approximately 2300 m. the percentage of ablation caused by radiation is only 58 to 65 per cent. This is primarily the result of the shortened duration of sunshine in the deeper valleys. The supply of perceptible and latent heat from the air can, at most, reach a value of 15 to 30 per cent on glacier tongues. Evaporation from the ice and heat supply by liquid precipitation are negligible during the normal ablation period (June till September).

It is to be expected therefore that the alpine glaciers will primarily react to variations of radiation and albedo during the months of June to September. The effects of changing summer temperatures are considered insufficient to cause the vast changes of the ice-cover. The variations of the duration of summer sunshine and the number of days with snowfall as a rough indication of albedo, respectively, are in perfect agreement with the behaviour of alpine glaciers during the last sixty years.

The distribution of fine banding (foliation) on the surface of a flat glacier tongue was studied. The conclusions reached are that fine banding seems to be neither of sedimentary origin nor to be the representation of a straightforward stress system. In the present case, foliation seems to be connected with ice falls.

Other bands definitely not belonging to the fine banding system were plotted irrespective of their outward appearance. Statistically, their preferred spacial directions correspond to the directions of either maximum shear stress or maximum normal stress (tension).