The use of mechanical transport, and the replacing of the old-fashioned methods of travel by plane or tractor, is a new feature of polar exploration. As will be seen in the following articles, each one by a specialist, the use of tractors is still, in most cases, at the experimental stage; but great advances have been made since Captain Scott took motor-sledges to the Antarctic in 1910.

On the Byrd Antarctic Expedition II a third mode of transportation was added to the existing means of dogs and aircraft—the use of tractors. Previous attempts had been made to use motor transport, first on Shackleton's Expedition in 1908, Scott's in 1910, and on the Byrd Antarctic Expedition in 1928–30. Shackleton had taken a regular motor car, which was of use on the hard bay ice, for handling supplies, but it proved inadequate for the softer surface of the barrier. Scott used special tractors, but they were not a success.

In 1929 Adolf Hoel summarised Norwegian Arctic work in Skrifter om Svalbard og Ishavet, No. 1, “The Norwegian Svalbard Expeditions, 1906–1926”. In the recently issued No. 73 of the same series, “Report on the Activities of the Norges Svalbard-og Ishavs-undersøkelser, 1927–1936” (125 pages, photographs and map), Dr Hoel likewise summarises the work of the following decade. The format of the report is that of the earlier issue with minor modifications, including, besides summaries of the work done year by year, such interesting and miscellaneous information as the finances of the various expeditions sent out, the names of the foreign expeditions that have been helped by the N.S.I.U., and many other kindred topics. In addition there are lists and tables that show in brief a mass of information on surveys and survey methods, the ships used, the papers and maps published and so on. The major part of the new report is devoted to a chronological statement of the expeditions sent out to Svalbard and East Greenland, and of the work at home. The arrangements of the reports on both these regions is similar, and the uninitiated might imagine that the ownership of Svalbard and East Greenland is the same. Each expedition account starts with the name of the ship used and the personnel, then follows a brief narrative of the venture, and finally there is a summary of the work done. The great value of this Skrifter, No. 73, lies in the provision it makes for ready reference. It is equally simple to find out where an individual worker has been and what was his work, what ships have been used and where, what papers and maps have been published and when, as it is to read precisely what a certain expedition was able to do in a particular year.

In the 1938 edition of Hints to Travellers, vol. ii, the editor has produced a handbook on travel rather than a collection of hints, and the general standard is now more comparable with vol. i. The work is the result of the editor's tireless energy and passion for details, combined with a selection of opinions from those who have travelled and explored in most of the relatively unknown parts of the world.

Modern polar research calls for a much more specialised and efficient travel technique than did polar exploration of even a few years ago; and, as a result, great strides have been made in perfecting the modern mechanical methods of transport. The old method of dog-sledging, with its comparatively low speeds and light loads, is already being replaced, to some extent, by mechanically driven sledges and aeroplanes. Several expeditions at work in the Arctic and Antarctic during the last few years have been able to make excellent use of air transport, but the first mechanically driven sledges were at best only moderately successful, and each reached its limit according to its construction either as a result of bad ice, slush, or deep powder snow, where the wheels or caterpillar band became bogged.

The Discovery II left St Katharine Dock on October 7, 1937. She will be away for twenty months continuing her research on the distribution of whales, hydrology and plankton.

The first seven months (the southern summer) are to provide data for comparison with those obtained on the winter circumpolax cruise of 1932 and with those of the survey of the southern part of the Pacific Ocean in 1934. The work was to have been done in 1935-36, but it was not completed as it was necessary to revise the programme after a voyage had been made to the Ross Barrier to pick up the American airman, Mr Lincoln Ellsworth.

Mechanical transport was first used by the author of this article at the time of the investigation of the Norilsk mining field (Lat. 69° 20′ N., Long. 88° 8′ E.) in 1925 for the purpose of taking goods from the port of unloading to the village of Dudinsk on the River Yenisei over a distance of 85 km. across tundra. At that time the tractor industry had only just come into being in the Soviet. Special machines for cross-country freight did not exist, so imported caterpillar tractors of the Reno make were used, drawing sledges freighted up to five tons. Certain constructional defects in the machines, and particularly in the sledges, as well as lack of experience in the work, combined to make the results far from satisfactory at this stage. At the end of the winter we had only succeeded in making one full journey and had transported only ten tons of profitable cargo on three machines. Nevertheless, this first experiment was valuable in that it demonstrated that, given mechanical improvement, the tractors might revolutionise polar transport. In this case, for instance, three machines had transported rapidly a cargo which would have required a caravan of two hundred and forty reindeer. It was ascertained also by this trial that caterpillar tractors of this type were suitable only for work in the vicinity of a base on smooth and hard roads. For transport over long distances in new and soft snow they were less satisfactory.

The Royal Research ship, Discovery II, arrived at St Katherine's Dock, London, on July 4, thus completing her third commission, like the others of twenty months' duration so as to cover two Antarctic summer seasons. The scientific work has this time been in the charge of Dr N. A. Mackintosh, with Mr H. F. P. Herdman as chief hydrologist, and Lieutenant A. L. Nelson, R.N.R., in executive command.

The publication of a Report on the Progress of the Discovery Committee's Investigations (Discovery Committee, Colonial Office, June 1937) provides a suitable occasion to review briefly the achievements of the last twelve years.