North Col
Mallory was taken ill and so it was left to Bullock to head on west to the head of the Kharta glacier on 13 August. However, a runner came back very soon to tell Mallory that Bullock had observed that the glacier ended in a high pass ahead. He would explore further but it was looking as if the glacier from the North Col did not flow east. Bullock returned and Howard-Bury received a letter from Wheeler showing the results of his survey – the glacier flowing down the east side of the North Col turned sharply north and joined the main Rongbuk Glacier. Time was too short to return to Rongbuk, which now seemed clearly the best way to the North Col, so they decided the best thing to do was to prospect a route to the pass Bullock had seen, which they called Lhakpa La ("Windy Gap") to see whether the North Col could be reached in this way. The weather was bad and the glacier was treacherous but eventually they reached the Lhakpa La on 18 August. Mallory decided the route was feasible and so it was agreed the reconnaissance could be concluded. They returned to base camp for ten days' rest.