In regions periodically subjected to falls of snow, major obstacles to the movement of men and vehicles are caused rather by the formation of drifts than by the uniform deposition of snow. Even in countries where snow-fall is not heavy, drifting can occasionally cause a breakdown of transport over a large area. Drifts form when snow-bearing winds meet obstacles which cause eddies in the wind stream and a local reduction in wind speed. The snow is deposited out of the wind stream into these regions of comparative calm, and the process continues for as long as an obstacle is effective in reducing wind speed.

Scurvy was known from the earliest times as a condition likely to arise when men were constrained to live upon a limited diet because of crop failure, siege or extended voyaging. It was first clearly described in the thirteenth century but, although its connexion with restricted supplies and especially with paucity of vegetables and fruit in the diet, was recognized from that period, its occurrence was ascribed to many other factors. Thus, because it often affected many members of a closed community at about the same time, it was thought to be contagious; and although conditions such as cold, the diminution of daylight in polar regions and the constant humidity of sea voyages were the reason for lack of fresh fruits and vegetables, these conditions themselves were suggested as causes of the disease. Likewise poverty, resulting in overcrowding and insanitary conditions, was blamed, whilst in reality economic conditions prevented the poor from buying antiscorbutic foods.

Much of the information given in the following description of techniques of glacier tunnelling is fundamental engineering knowledge and is included specifically for the benefit of glaciologists. Numerical results and their interpretation are omitted; a preliminary report concerning them has been published (McCall, 1952).

The following article does not describe the winter war which followed the Soviet attack upon Finland in 1939, nor the campaign brought about by the German invasion of Norway in 1940. It deals with the military operations in arctic Europe which followed the German attack upon the U.S.S.R. in 1941, ending with the German capitulation in 1945. During the greater part of this period Finland was a co-belligerent of Germany against the U.S.S.R. In 1944, however, Finland was obliged to capitulate to the U.S.S.R. and then, by the terms of the capitulation, to turn upon the Germans and help the Russians to drive them from Finnish soil. The description of the military operations is based largely upon German accounts. Unfortunately no Soviet source of information is available.

Internal combustion engines, in common with all heat engines, derive their capacity for work from a cycle of operations which comprises the supply of heat at a high temperature followed by the rejection of heat at a much lower temperature. The difference between the two quantities of heat represents the maximum amount of energy which can be converted into useful work. In the familiar piston-type internal combustion engine, the heat supply is maintained by burning a suitable fuel in air, and heat is rejected largely in the exhaust gases. With heat engines in general, it is true that the higher the temperature of the heat supply, the greater the efficiency of the engine. There are, however, limitations to the temperature at which an engine can operate. These are imposed by the properties of the materials used in its construction, and by the necessity of maintaining satisfactory lubrication in all circumstances.

The Greenland ice sheet, the area of which is some 1,870,000 sq.km., between three and four times that of France, has remained largely unknown until the present time. Between 1948 and 1951 extensive investigations were made by Expéditions Polaires Françaises (Missions Paul-Émile Victor), relying largely upon new methods of transport which had been developed, particularly in North America, during the Second World War. Perhaps the most important of these were the use of the amphibious tracked vehicle known as the Weasel (Light Cargo Carrier M29C, manufactured by the Studebaker Corporation) to transport men and equipment over the ice sheet, and of aircraft to drop supplies to the ground parties, so that their radius of action could be greatly increased. During the course of the expedition the Weasels covered a combined total distance of approximately 85,000 km., and from 1949 to 1951 a well-equipped scientific observation post, known as the “Station Centrale de Recherches” was maintained in the centre of the ice sheet in lat. 70° 55′ 3″ N., long. 40° 38′ 22″ W. These achievements were made possible by the use of aircraft to drop a total of some 230 tons of stores and equipment on the ice sheet.

The first sea-ice forecast for waters north of the U.S.S.R. was issued in 1923, and since about 1935 more than a dozen Soviet scientists have been studying the question. Before any method of forecasting could be evolved, meteorological and oceanographical observations, and information on the state of the sea ice had to be available. This information was collected by polar stations, merchant ships, icebreakers, vessels on patrol duty at the ice edge and aircraft on ice reconnaissance. In the late 'thirties, however, forecasters were still complaining of lack of data; not necessarily because they thought the system of collecting information was inefficient, but because there were so few observations for the preceding period. Nevertheless, a number of correlations were advanced and tested. As time went on and the volume of observations grew, it became possible to elaborate principles of more general application. This was done for instance by V. Yu. Vize, one of the earliest investigators of the subject, in a monograph called Osnovy dolgosrochnykh ledovykh prognozov [Principles of long-term ice forecasting]. The work was awarded a Stalin prize in 1946, but apparently no copy has come out of the U.S.S.R. It is not possible, therefore, to examine the methods which have been developed by Soviet scientists on the basis of ten to fifteen years' observations, but the earlier ideas which are considered below no doubt form the basis of the later system.

Knowledge of this unsuccessful voyage is somewhat fragmentary, and most of the narrative has been pieced together from correspondence which passed between Messrs Enderby Brothers and the Admiralty. Former writers1 believed that John Biscoe, originally nominated to command the expedition, sailed from London in the Hopeful. It has also been supposed that Biscoe resigned his command when the ships reached the Falkland Islands.

The spade, or snow shovel, is an item of equipment required by any community living in the snow, particularly in the accumulation area of an ice sheet, where any object placed on the snow is eventually buried beneath a continually rising surface. Roald Amundsen, Alfred Wegener, R. E. Byrd, A. R. Glen and others have described the hours and sometimes days spent by members of their expeditions moving snow by hand. The Norwegian-British-Swedish Antarctic Expedition, 1949–52 was no exception. Some shovelling is unavoidable, being a consequence of natural accumulation, but much results from the burial of stores and equipment under snowdrifts caused either by the objects themselves or by their neighbours.

Of the sixty-two sledge dogs helonging to the Norwegian-British-Swedish Antarctic Expedition, twenty-eight dogs came from Jakobshavn and Christianshåb in West Greenland, twelve from Longyearbyen in Spitsbergen and twenty two (including nine bitches) from the Falkland Islands Dependencies. The dogs from Spitsbergen had originated in Canada in 1945; those from the Falkland Islands Dependencies had been bred from dogs originally brought from Labrador in 1945 and 1946. The dogs from Spitsbergen were larger than the others, and several weighed considerably more than 50 kg. The dogs from West Greenland and the Falkland Islands Dependencies were smaller, averaging 40 to 50 kg. At the time when they were acquired by the expedition, the dogs from Spitsbergen and the Falkland Islands Dependencies were in much better condition than those from West Greenland.