The distribution of temperature throughout an ice sheet has been considered, taking into account the influence of ice movement as well as other items previously considered, such as conduction, the geothermal outflow of heat and heat generated by ice movement. By making certain simplifying assumptions, a quantitative method of estimating the temperature distribution near the centre of an ice sheet has been put forward.

It is shown that even a small mean annual accumulation will have considerable effect on the temperature distribution in a large ice sheet. For a moderate rate of accumulation a substantial fraction of the total thickness of ice at the centre of a large ice sheet may be isothermal at the prevailing surface ice temperature. Under these conditions at some distance from the centre, the change in the surface ice temperature with elevation may produce a temperature gradient opposite to normal, that is the temperature falls with increasing depth below the surface, due to the outward movement of the ice. Observed temperature gradients on ice sheets fit the proposed hypotheses roughly, but it appears that climatic change should also be taken into account.

It is suggested that a rise from temperatures below melting point at the base of ice sheets may provide an explanation of the occasional catastrophic advances of certain glaciers.

A mixture of approximately one part of water to two parts of kaolin (china clay) has proved suitable for making model glaciers on scales between 1 : 1000 and 1 : 10,000. The kaolin “glaciers” crevasse and flow realistically, and slide on their beds. They serve well for qualitative demonstrations, and some simple preliminary quantitative experiments suggest that they may also be useful for this purpose.

Firn and ice thickness measurements were carried out by seismic refraction and reflection methods on a flat col of the highland snowfields of the Penny Ice Cap and on a medium-sized valley glacier (Highway Glacier). The longitudinal wave velocities were found to vary from some 1000 m./sec. (3280 ft./sec.) in firn to 3810 m.,/sec. (12,500 ft./sec.) in ice and approximately 6000 m.% sec. (20,000 ft./sec.) in the bedrock (gneiss). The thickness of firn and ice at the firn col was found to be 254 m. (834 ft.). On Highway Glacier some 80 reflections were evaluated, giving position, dip and strike of the bedrock surface. A longitudinal profile of Highway Glacier from the junction of three main tributary glaciers to the tongue is given; the ice thickness slowly decreases. At the junction, the bedrock is 400 m. (1310 ft.) deep, there is no deep basin as might be expected from the surface features. The mean slope of the glacier surface is about 3° of arc and of the bed about 1°.

Density of single crystals of ice from the Mendenhall Glacier near Juneau, Alaska, a temperate glacier, was determined by the hydrostatic weighing method. It was found that the densities of single crystals are slightly but measurably variable from one crystal to another. The values range from a minimum of 0.91712 gm./cm.3 to a maximum of 0.91728 gm./cm.3, when corrected for −3.5° C., for the eight crystals measured. Any imperfections such as Tyndall figures (hexagonal prismatic voids) were immediately evident in the density determinations, and correction for these imperfections give a corrected density essentially the same as that of clear specimens. Two clear crystal aggregate specimens tested had a lower density than the pure single ice crystals. An error computation gives the value of the estimated maximum error of the density determinations as ±2.1×10−5 gm./cm.3.

Two Eppley pyrheliometers were used to measure incoming and reflected sun and sky radiation over a saturated, melting snowpack. Albedo values computed from these measurements varied strongly, not only with snow surface conditions, but also diurnally with the angle of the sun, and from clear to cloudy skies. On clear days minimum albedo in the afternoon was approximately 35 per cent less than the maximum in early morning; a secondary maximum occurred at sunset. Also, midday albedos were higher under cloudy skies than under clear skies. These variations appear to relate primarily to changes in angle of incident radiation, and secondarily to changes in the physical structure of the snow surface. Spectral changes in incident radiation are also a possible factor.

Accumulation and ablation measurements on Morsárjökull are described and a tentative glacier budget for the three seasons 1951–52, 1952–53 and 1953–54 is presented. Observations of glacier flow on Morsárjökull, Svinafellsjökull and Skaftafellsjökull are considered. The recent fluctuations of the snouts of Skaftafellsjökull and Svinafellsjökull are discussed and related to variations in the height of the accumulation zones of the glaciers; recent glacier thinning is also mentioned.

In the approximately so m. thick ice cap of the Jungfraujoch (3470 m. above sea level), where the temperature throughout lies below the pressure melting point, continual measurements of displacement and deformation were carried out inside ice tunnels from 1950 onwards. These give an insight into the process of movement, the formation of water-filled crevasses and the relationships of viscosity in a cold ice cap glacier.

The plastic behaviour of the cold ice was examined through alterations in length of individual tunnels, and also through measured distortions of cross-section in circular sections of tunnel. Since the mean ice temperature in the region of the ice tunnel lies approximately between −1° and −3° C., these examinations provide a welcome supplement to analogous measurements which were taken in circular tunnels in a temperate glacier (Z’Mutt tunnel). The approximate calculation of the plastic deformation of a circular tunnel was thus extended by the obvious transformation of solutions known from elasticity theory.

By means of a qualitative analysis of the state of stress of an ice cap, an attempt is made to account for the distortion and the formation of the cracks and crevasses which were observed. The occurrence of blue bands could be followed in statu nascendi. This paper serves as a primary orientation and publishes some initial results of the examinations which are to be continued and completed over a number of years. In addition to its potentialities for practical use, this study may be of interest in respect to the behaviour of cold glaciers of the Arctic and Antarctic. In a final section, therefore, some problems of the Greenland ice sheet are considered in the light of the preceding conclusions.

Description of a horizontal tunnel driven through a cold, steeply sloping glacier, altitude 14,000 feet (4267 m.) on Monte Rosa, from its surface right through to bedrock, a distance of 302 feet (42 m.). Temperatures found deep within this cold glacier were 18° F. (−7.78° C.) compared with 8° F. (−13.33° C.) near its surface, and again near contact with its rock bed. This internal heat is interpreted as heat supplied from the interior of the earth, and as indicative of existence of ice at pressure-melting-point in all cold ice glaciers, if thickness of ice is sufficient. Existence of such an underlay of ice at pressure-melting-point, varying in distribution with varying supply of internal heat, is shown to explain (1) cirque erosion, (2) uniform elevation of cirques in any one region, (3) existence of extrusion flow under certain conditions, and (4) control of cycles of continental glaciation, under extreme limits.

The horizontal and vertical motions of eight points on the surface of Highway Glacier, Baffin Island are reported. The average horizontal speed below the lowest tributary glacier is 56 metres/year. The major part of this motion arises from the glacier sliding on its bed. The mean shear stress on the bed is practically constant and equal to about 0.9 bars, but it is much smaller beneath the retreating tongue. A measure of the retreat in the lower part of the glacier is obtained from the difference between the ice discharge and the net ablation.

Mt. Ruapehu, the highest summit in the North Island of New Zealand, is a semi-dormant volcano, whose crater lake was responsible for the flood that caused the disastrous railway accident on Christmas Eve, 1953. Since the last eruption of 1945, when mostly ash was ejected, the crater lake that subsequently formed has been contained by a barrier partly composed of lava and partly of névé and ash. It was the breaking through of the latter weaker portion of the dam that was responsible for the flood of mud and boulders which descended via the Whangaehu Glacier and struck the railway 25 miles (40 km.) distant. There is no evidence of eruptive activity having been the cause of the outbreak. During three ascents of the mountain, observations were made of the glaciers, which have been in a state of gradual shrinkage over a number of years. But during the past Summer—a season of exceptional dryness—the process of ablation and wastage has been greatly accelerated, so that immense areas of rock and ash have freshly emerged, and crevasses and dirt-ridges have taken the place of smooth névé or glacier surfaces.