The existence of high rock thresholds beneath the glaciers of Dronning Louise Land is established and examples are described. It is concluded that decrease in the height of the Greenland Ice Cap and the consequent emergence of the rock thresholds is the dominant factor in the final stages of recession of the glaciers of Dronning Louise Land. It is tentatively suggested that this process has more than local significance, and may be an important factor in the recent recession of the glaciers in other parts of east Greenland.

The Coleman Glacier on Mt. Baker in the State of Washington began to advance about 1949 after a long period of rapid retreat. Since that year the terminus has advanced continuously a total of about 300 m. and considerable thickening of the entire glacier has occurred. The continued advance of the Coleman Glacier and other evidence are interpreted as manifestations of a trend during the last decade towards a slightly cooler and moist climate in the north-west of the United States.

It has been found that in the cold firn of the Greenland Ice Sheet a direct relationship exists between the specific gravity of a layer and its “resistance to penetration” as measured with a Rammsonde. Corrections which should be applied to the measured “resistance” to allow for the frictional resistance of the walls of the hole on the Rammsonde tube are discussed. In certain circumstances these corrections can be estimated with reasonable accuracy for tube lengths up to three metres. The statistical method of obtaining the relationships between “resistance” and specific gravity is briefly outlined, and the effect of the size of the snow grains is also considered. It is shown that under these particular conditions it is possible, from measurements of “resistance”, to estimate the specific gravity of a firn layer with a standard error of 0.04, when the specific gravity of the sample is in the range 0.3 to 0.57.

The hardness observations taken in the Canadian Snow Survey are analysed and found to depend on snow density, temperature, and crystal size. This strength property of the snow is found to be highly variable and the variability is attributed to unstable bonding between individual snow grains.

The structure of some moraines in and around two glaciers in northern Norway was studied by the method of fabric analysis. It was found that englacial material tends to lie parallel to the direction of movement of the ice, and material in lateral and terminal moraines shows orientations which appear to be related to the conditions under which it was deposited.

During the Cambridge Austerdalsbre Expedition 1955, a tunnel was dug horizontally into the ice at the foot of a large ice fall, and its subsequent movements were surveyed. The axis of the tunnel was rotating very fast, as might be expected from the change in surface slope under the ice fall, but as well as this the tunnel was being bent, i.e. the tunnel axis was an active anticline. As the local surface of the glacier above the tunnel was convex, this bending was tending to increase the convexity, and as it is in this region that waves form across the glacier under the ice fall this observation is interpreted as showing that the wave ogives are actually being formed in the ice surrounding the tunnel. The distances between pegs in the tunnel walls were also measured. There was a compressive strain occurring along the tunnel axis (i.e. the tunnel was decreasing in length) and the tunnel was also closing far more rapidly than would be predicted from the weight of overlying ice alone. These two observations suggest that a large compressive stress is acting in the glacier in a longitudinal direction. Measurements on surface stakes, though not of the same accuracy as the internal measurements, confirmed these predictions, and also allow the strain rate tensor to be estimated. From this the magnitude of the stresses can be computed, and the longitudinal compressive stress is estimated to be about 3 bars. Observations of the banding on the walls of the tunnel showed that the fine bands were within 10° of being perpendicular to the maximum compressive stress.

The lecture was a review of the research work carried out by the author and his collaborators, as well as by J. Gjessing and students working for their final degree. Attention is called to the existence of local centres in western regions even during the maximum of the last glaciation, as well as the transition from down-wasting of dead ice near the ice divide to backward melting of partly active glacier tongues in the high mountains near the sea. Regional reconstructions of the waning of the glacier ice are attempted.

A method is described of determining the thickness of a valley glacier from measurements of gravity. On a Norwegian glacier approximately 4 km. long and km. wide values of gravity were measured at points on four transverse lines. For comparison, values were measured at points on three lines in the valley below the snout of the glacier. The positions and altitudes of these gravity stations were determined by triangulation. After making corrections for the altitudes of stations and for the effect of the valley walls, the differences between the gravity values obtained on the glacier and those obtained in the valley below the glacier are attributed to the thickness of the ice. Four transverse sections of the glacier, obtained in this way, are given. Errors in the estimates of ice thickness should not exceed 20 per cent on the two lower cross-sections, nor 40 per cent on the upper two.

Thermograph, thermistor, and thermometer readings at a 30 m. deep bergschrund from June 6 to July 22, 1953, showed that there was little direct relationship between air temperatures outside and at the bottom of the Schrund. The air temperature inside ranged from −3.7° C. (253° F.) to +0.5° C. (32.9° F.), but from July 2 onwards it oscillated between –0.5° C. and +0.5° C., with a 3–4 day periodicity. The ice temperature at the bottom of the schrund behaved similarly, though it was about 0.5° C. colder. The oscillations may have been caused by the interplay of flowing melt water (source of heat) and air drainage in quiet weather (source of cold). The granite-gneiss headwall, where not sheathed by refrozen melt water, appeared to be chemically and mechanically unweathered, which supported the conclusions of Battle’s earlier tests in deep bergschrunds and in the laboratory.