From the Lhakpa La the mountaineers were now looking straight at Everest, and at last were able to unriddle its tangled topography. The attention of the reader is called to the map. It will be seen that the great Rongbuk Glacier, which descends from the western side of the northern face, receives as a feeder the East Rongbuk Glacier. The entrance to the latter is so small that Mr. Mallory and Mr. Bullock had failed to notice it in their exploration of the main glacier. This lesser Rongbuk Glacier ends on the eastern part of the northern face of the mountain, and between its head and that of the main glacier is the pass called the Chang La, or North Col. From the Lhakpa La one looks into the East Rongbuk Glacier with the North Col straight in front. If the North Col could be attained, it seemed to the mountaineers to be possible, by working up the easy northern face, to attain the North-East ridge at a point above the main difficulties.
The camp on the Lhakpa La was not a comfortable place, with a howling wind, 34 degrees of frost, and little stuffy tents which gave dubious protection and inevitable headaches. It was decided that the two expert Alpine climbers, with a few picked coolies, should alone attempt the North Col, and, if fortune favoured, prospect the farther route, while the others returned to the 20,000-feet camp.
We are now concerned with the doings only of Mr. Mallory and Mr. Bullock, who were to attempt the North Col. In the weeks since their arrival in the neighbourhood of Everest they had been studying its contours with the eyes of trained mountaineers. They saw that it was a great rock mass, "coated often with a thin layer of white powder, which is blown about its sides, and bearing perennial snow only on the gentler ledges and on several wide faces less steep than the rest." They saw that from the point of the North-East shoulder a more or less broad _arête_ fell northward to the snow col called the Chang La. If they could reach that snow col the road to the North-East ridge looked reasonably simple. They had seen that the Chang La would be very difficult of attainment from the Rongbuk Glacier, and that was why they had turned their minds to an eastern approach. Here is their conclusion, in Mr. Mallory's words, reached about the third week in July: "If ever the mountain were to be climbed, the way would not lie along the whole length of any one of its colossal ridges. Progress could only be made along comparatively easy ground, and anything like a prolonged sharp crest or a series of towers would inevitably bar the way, simply by the time it would require to overcome such obstacles. But the North _arête_, coming down to the gap between Everest and the North Peak, Changtse, is not of this character. From the horizontal structure of the mountain there is no excrescence of rock pinnacles in this part, and the steep walls of rock which run across the north face are merged with it before they reach this part, which is comparatively smooth and continuous, a bluntly rounded edge.... The great question before us now was to be one of access. Could the North Col be reached from the east, and how could we attain this point?"