Another great question remained unsolved. We had been able to make out the way across the head of the glacier towards the wall under Chang La; and the way was easy enough. But the wall itself, in spite of some fleeting glimpses and partial revelations, we had never really seen. We conjectured its height should be 500 feet or little more; and it was probably steep. It had been impossible to found an opinion as to whether the col were accessible. Nevertheless, I held an opinion, however flimsy the foundations. I had seen the rim of the col from both sides, and knew that above it on either hand were unserrated edges. When we added to whatever chances might be offered by the whole extent of the wall, which was considerable, the possibilities of finding a way to the col by the slopes of Everest to the South or by those of Changtse to the North, I felt we had enough in our favour. I was prepared, so to speak, to bet my bottom dollar that a way could be found, and was resolved that before we turned homewards this year we must get up from the East. When I thought of the 4,000 feet on the other side, the length combined with the difficulties, the distance that would necessarily separate us there from any convenient base and all the limitations in our strength, I could have no reasonable doubt that here to the East lay the best chance of success. [Illustration: NORTH-EAST OF MOUNT EVEREST AND CHANG LA from Lhakpa La.] It remained to determine by which of two possible routes we should reach the glacier-head between Lhakpa La and Chang La. Presuming that Wheeler was right we could use the old base at the foot of the Rongbuk Glacier which was only one stage, though a very long one, from Choebuk, and proceed simply enough by two rough marches and one which should be easier to a camp at the foot of the wall or possibly to the col itself. On the East we could use as an advanced base a place two easy marches from Kharta; from there I reckoned one long day and two easy ones, provided the snow were hard, to Chang La. Against this route was the loss of height in crossing Lhakpa La; and for it the convenience of a good encampment on stones at 20,000 feet, better than anything we might expect to find at a similar elevation on the other side. So far the pros and cons were evenly balanced. But there was one great and perhaps insuperable obstacle in working from the Rongbuk Valley. We had always found difficulties there in obtaining an adequate supply of fuel. There is no wood at Choebuk or for some distance below it. A few small bushes grow in a little patch of vegetation by the riverside an hour higher up. But it is a very niggardly supply, and when I thought of the larger scale of the preparations we should now have to make, it became clear that we should have to rely on gobar, which, besides being a more extravagant fuel in the sense that it gives less fire for a given weight than wood, is also difficult to get in the Rongbuk Valley, for little