Quite early in the exploration of Mount Everest it was obvious that if the 23,000-foot col could be reached, most of the physical difficulties of the approach to the mountain would have been surmounted. But it was not so obvious how to win to the col. It lies on the South-east at the head of the main Rongbuk Glacier; it was therefore to this glacier that the mountaineers, Messrs. Mallory and Bullock, went from Tingri Dzong on June 23. They spent a month exploring the country to the North and the West of Mount Everest from the Rongbuk Glacier. Much valuable information was accumulated. A peak, Ri-Ring, 22,520 feet, was climbed and a pass on the West ridge of Mount Everest was visited, from which were seen views of the South-west face of the great mountain and also many high peaks in Nepal. Unfortunately, however, no feasible route from the main Rongbuk Glacier to the 23,000-foot col could be found. The next attempt was made by leaving the Rongbuk Glacier and exploring the Kama Valley that flows South-east from Mount Everest. Here a most magnificent ice-world was discovered. For a chain of giant peaks running South-east from Mount Everest to Makalu, 27,790 feet, guards the whole of the South-west side of the valley. But as an approach to the North-east arete of Mount Everest this valley was found to be useless. From the point of view, however, of exploration it was most fortunate that this valley was visited. The photographs of Makalu and its satellite Chomoloenzo, N.^{53}, 25,413 feet, are superb; moreover the lower reaches of the Kama Valley, as it dips down to the deep Arun Valley, was full of luxuriant vegetation, totally different from the wind-swept wilderness of Tibet. The Kharta Valley, that runs North-east from Mount Everest, was the next exploited, to see whether from it an easy approach to the North-east arete existed. But by this time the monsoon weather was at its worst. Days of rain and mist, with snow higher up, succeeded one another, making climbing impossible. However, towards the end of September a high camp at 22,500 feet was made at the head of the Kharta Valley. From this camp the 23,000-foot col, Chang La, was finally reached, by crossing the head of a glacier that ran to the North. Higher climbing was out of the question; a furious North-west gale lasting for four days drove the party off the mountain. The glacier mentioned above, running to the North, was found to be a tributary of the main Rongbuk Glacier, and has been named the East Rongbuk Glacier. There is no doubt that the easiest route to Chang La, the North Col, will not be all the way round by the Kharta Valley, but up this East Rongbuk Glacier.