What was called the Advance Base Camp was established in the Kharta valley at a height of 17,350 feet, in a grassy hollow well sheltered from the wind, and amid a glory of Alpine flowers. Meantime Mr. Mallory and Mr. Bullock spent their time in carrying wood and stores to a camp higher up the valley. This was finally established at a height of some 20,000 feet, well up the Kharta Glacier. At the glacier head was a pass called the Lhakpa La, or "Windy Gap," and the next step was to form a camp there at a height of 22,350 feet. It was in this neighbourhood that the tracks, probably of a wolf, were found, which the coolies attributed to the "Wild Men of the Snows." 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.