The other occasion when we had to face and determine the possibility of an avalanche was in traversing the slopes to the North Col. Here our feet undoubtedly found a solid bed to tread upon, but the substance above it was dubiously loose. It was my conviction at the time that with axes well driven in above us we were perfectly safe here. But on the way down we observed a space of 5 yards or so where the surface snow had slid away below our tracks. The disquieting thoughts that necessarily followed this discovery left and still leave me in some doubt as to how great a risk, if any, we were actually taking. But it is natural to suppose that at a higher elevation or in a cooler season, because the snow adheres less rapidly to the slopes on which it lies, an avalanche of new snow is more likely to occur. TEMPERATURE Before attempting to draw conclusions as to the relative chances of finding favourable conditions between one month and another, a few words must be said about temperature. So far as the temperature of the air was concerned, we experienced no severe cold and suffered no hardships from first to last. I do not mean to affirm that it was always warm. We welcomed frost at nights as one does in the Alps. One night so early as July 18, in a camp above 19,000 feet, was exceptionally cold. At our two last camps in September the thermometer went down to two or three degrees below zero (Fahr.) and the wind at the final camp made it more difficult to keep warm; with as little protection as the coolies had, I should no doubt have shivered in my tent. The air also seemed very cold before sunrise on September 20, though we were walking fast; but it did not bite the tip of my nose or ears or cause any disagreeable result. In general it may be said that there could be no difficulty in providing equipment against any cold we encountered. Heat was a much more dangerous enemy, as I indicated in describing our first ascent to Lhakpa La. Personally I never felt the sun's power on my head, but I felt it on my back so early as 8 a.m. as a definite attack on my energy and vital power, and more than once, though the sun was not shining, in crossing a glacier late in the day I was reduced from a state of alert activity to one of heavy lassitude.