The transport question must always be difficult. The thousand feet from the East Bongbuk Glacier to the Chang La, half of which was very steep, might give trouble to laden coolies, especially earlier in the season when the ice was uncovered by snow. An advanced base camp on the Chang La would, of course, be essential if a high camp were to be made at 26,000 feet. But the physical problem might be regarded as solved--at any rate as far as the shoulder of the North-East _arête_. On the physiological question little light had been thrown. The climbers in September 1921 were all more or less tired from spending long periods in high camps, and could not be regarded as at the top of their form. Yet in the case of most members of the party the process of acclimatization had been rapid, and Mr. Mallory on the Chang La was remarkably fit. What would happen, however, at the higher altitudes? The effect of these upon the human body had not been decided. The conclusion from the year's work was that while no insuperable difficulty had been proved in the problem, yet for success there must be a combination of happy chances in the shape of weather, the condition of the snow, the endurance of the transport coolies, and the bodily fitness of the climbers. A second attempt would be justified, but it could not be regarded with anything like confidence. The enterprise was seriously and responsibly envisaged, and no better expression of the spirit of those who undertook it can be found than in Mr. Mallory's own words: "It might be possible for two men to struggle somehow to the summit, disregarding every other consideration. It is a different matter to climb the mountain as mountaineers would have it climbed. Principles, time-honoured in the Alpine Club, must, of course, be respected in the ascent of Mount Everest. The party must keep a margin of safety. It is not to be a mad enterprise, rashly pushed on regardless of danger. The ill-considered acceptance of any and every risk has no part in the essence of persevering courage. A mountaineering enterprise may keep sanity and sound judgment, and remain an adventure. And of all principles to which we hold, the first is that of mutual help. What is to be done for a man who is sick or abnormally exhausted at these high altitudes? His companions must see to it that he is taken down at the first opportunity, and with an adequate escort; and the obligation is the same whether he be sahib or coolie. If we ask a man to carry our loads up the mountain, we must care for his welfare at need." III