It will be understood from this method of calculation how we arrive at the number of loads which must be carried up to any given camp; it is observable that at each stage downwards the number increases in a proportion considerably greater than 2:1. Fortunately we are not obliged to proceed strictly on these lines; to the lower camps we need not carry up the whole of our stores on one day, and consequently we need not increase in this alarming ratio the number of our porters. But in any case when we get down to the North Col we must clearly have a large bulk of stores; and the fewer porters we employ between one stage and another, economizing on tents and sleeping-bags, the more time we shall require. It was clear from the start that time was likely to be a formidable enemy. General Bruce’s problem was not only to move our vast quantity of stores across an almost barren country, but to move them in a given time. It was fortunate for this reason that the number of porters who came with us was not increased, for every man must add something to our burdens. No one who knows that arid country could fail to be surprised that we reached our Base Camp below the Rongbuk Glacier so early as the 1st of May. But now the number of Nepalese porters—only forty were available for carrying—was too small for all our needs. If they alone were to shoulder all our loads when should we reach the North Col? Some sort of depôt must be established below it at 21,000 feet for the supply of all higher camps on the mountain before we could proceed; and the reconnaissance party determined that two staging camps would be required between the Base Camp and this depôt. The existence and the solution of so large a problem of transport have so important a bearing on our later plans that I must refer to it again in this place. General Bruce has told how he impressed Tibetans into his service, and by using them up to Camp II was able to liberate our own porters much earlier than might have been expected for work further on. But the system of employing Tibetans did not work without a hitch. It was because the first labour battalion absconded that General Bruce gave orders for only two of us to go forward and use the first opportunities for pushing on from Camp III. With the prospect of an early monsoon and a shortage of transport it was desirable that, so soon as any porters were available for work above Camp III, this work should be pushed on without delay, and if necessary an assault should be made with the minimum of stores required by a party of two climbers. Without a further supply of transport there was no question of using the oxygen, for we should have more than enough to carry up without it.