No less important in this connection is the effect of exertions at high altitudes on a man’s subsequent performance. We have to take into account the condition of the climbing parties when they returned to the Base Camp after reaching approximately 27,000 feet. With one exception, all the climbers were affected in various degrees by their exertions, to the prejudice of future efforts. It would seem, therefore, that they cannot have had much strength to spare for the final stage to the summit. But there was a general agreement among the climbers that it was not so much the normal exertion of climbing upwards that was in itself unduly exhausting, but the addition of anything that might be considered abnormal, such as cutting steps, contending with wind, pushing on for a particular reason at a faster pace, and the many little things that had to be done in camp. It is difficult from a normal elevation to appreciate how great is the difference between establishing a camp on the one hand and merely ascending to one already established on the other. If ever it proves possible to organise an advanced party whose business it would be to establish at 25,000 feet a much more comfortable camp than ours in 1922, and if, in addition, a man could be spared to undertake the preparation of meals, the climbers detailed for the highest section of all would both be spared a considerable fatigue and would have a better chance of real rest and sleep. The peculiar dangers of climbing at great altitudes were illustrated by the experience of 1922. The difficulty of maintaining the standard of sound and accurate mountaineering among a party all more or less affected by the conditions, and the delays and misfortunes that may arise from the exhaustion of one of the party, are dangers which might be minimised by a supporting party. Two men remaining at the final camp and two men near Camp V watching the progress of the unit of assault along the final ridge, and prepared to come to their assistance, might serve to produce vital stimulants, hot tea or merely water, at the critical moment, and to protect the descent. It is a counsel of perfection to suggest providing against contingencies on this lavish scale; but it is well to bear in mind the ideal. And there is, besides, a precaution which surely can and will be taken: to take a supply of oxygen for restorative purposes. The value of oxygen for restoring exhausted and warming cold men was sufficiently well illustrated during the second attempt in 1922. [Illustration: CHANG LA AND NORTH-EAST SHOULDER OF MOUNT EVEREST ]