But about one point in the equipment of the party there was much diversity of opinion. Should the climbers be provided with oxygen, or should they not? If it were at all feasible to provide climbers with oxygen without adding appreciably to the weight they had to carry, the summit of Mount Everest could be reached to a certainty. For the purely mountaineering difficulties are not great. On the way to the summit there are no physical obstacles which a trained mountaineer could not readily overcome. The one factor which renders the ascent so difficult is the want of oxygen in the air. Provide the oxygen and the ascent could be made at once. But to provide the oxygen heavy apparatus would have to be carried—and carried by the climbers themselves. It became a question whether the disadvantage of having to carry a weight of at least thirty pounds would or would not outweigh the advantages to be gained by the use of the oxygen. And the Mount Everest Committee were warned of another feature in the case. They were told that if by any misfortune the oxygen were to run out when the climbers were at a considerable height—say 27,000 feet—and they suddenly found themselves without any preparation in this attenuated atmosphere, they might collapse straight away. It was a disagreeable prospect to anticipate. But Captain Finch, who was himself a lecturer on chemistry at the Imperial College of Science, Mr. Somervell, and Captain Farrar, pressed so strongly for the use of oxygen, and Mr. Unna was so convinced he could construct a reasonably portable apparatus, that the Committee decided that the experiment should be made. The value of using oxygen could thus be tested, and we should know what were the prospects of reaching the summit of the mountain either with or without its aid. Captain Farrar, Captain Finch, and Mr. Unna therefore set about constructing an apparatus which would hold the lightest procurable oxygen cylinders, and which could be carried on the back by the climbers.