Although it is true that at high altitudes there is less oxygen to breathe, the body rapidly protects itself by increasing the number of red blood corpuscles. These red corpuscles are the carriers of oxygen from the air to the various parts of the body. An increased number of carriers means an increase of oxygen to the body. It is just possible, therefore, that anyone properly acclimatised to, say, 23,000 feet would be able to ascend the remaining 6,000 feet, to the summit of Mount Everest. Moreover, if oxygen could be continuously supplied to the climbers by adventitious aid there is little doubt that 29,000 feet could be reached.
The physiological difficulties met with in ascending to high altitudes are doubtless of a very high order, but can to a certain extent be eliminated by ascending gradually, day after day, so as to allow the body to accommodate itself by degrees to the new surroundings.
There are, however, other difficulties that must be reckoned with, such as intense cold and frequent high winds. In any engine where loss of heat occurs, there is a corresponding loss of available energy. A bitterly cold wind not only robs one of much heat, but lowers the vitality as well. At altitudes above 24,000 feet, the temperature is often arctic, and the thermometer may fall far below zero. On the other hand, the rays of the sun are intense. The ultra-violet rays, that are mostly cut off by the air at sea-level, are a real source of danger where there is only one-third of an atmosphere pressure, as in the case at the summit of Mount Everest.
The mountaineer also encounters dangers in the Himalaya, on the same scale as the difficulties. A snow-slide on a British mountain or in the Alps is an avalanche; often in the Himalaya it becomes almost a convulsion of nature. The huge ice-fields and glaciers that hang on the upper slopes of the mountains, when let loose, have not hundreds of feet to fall, but thousands, and the wind that is thereby produced spreads with hurricane force over the glaciers below, on to which the main body of the avalanche has fallen. Sometimes even the broken débris will rush across a wide glacier.
Rock falls also assume gigantic proportions in the Himalaya. But all these dangers can be largely avoided by the skilled mountaineer, and he can choose routes up a mountain where they are not likely to occur. Some risks, however, must be always run, but they can be reduced to a minimum.
On Mount Everest, as we now know, most of these dangers will be less than on any of the other very high mountains in the Himalaya. Also there are no difficulties in the approach to Mount Everest from India. In this respect it differs from such peaks as K2 and others. As a rule the highest mountains in the Himalaya always lie far back from the plains in the main chain, beyond the foot-hills and the intervening ranges. To approach them from the South in India, weeks of travel are often necessary, up deep gorges, and over rivers, where it is next to impossible to take baggage animals. Fortunately the approach to Mount Everest by the route from Darjeeling to Phari Dzong and thence over an easy pass into Tibet avoids all these difficulties. In Tibet a high tableland, averaging 13,000 feet, is reached.
Travelling in Tibet, North of the main range of the Himalaya, is entirely different from that on the South of the range. Instead of deep-cut gorges, a rolling, bare, stone-covered country exists, over which it is easy to take baggage animals, the only obstacle being the rivers that sometimes are not bridged, and are often swollen by the melting snow. From Kampa Dzong to Tingri Dzong, the base of operations for the Expedition, is an open country. Mount Everest lies 40 to 50 miles South of Tingri Dzong; the approach also is without difficulty.
The ascent of Mount Everest was not the primary object of the Expedition of 1921. A mountain the size of Mount Everest cannot be climbed by simply getting to it and starting the ascent immediately.
A reasonable route has to be discovered to the summit; which usually can only be done by a complete reconnaissance of the mountain. This has been admirably done, and a most magnificent series of photographs has been brought back by the members of the Expedition.
Mount Everest consists of a huge pyramid, having three main arêtes, the West, the South-east, and the North-east. It is the last, the North-east arête, that is obviously the easiest, being snow-covered along most of its length. Nowhere is it excessively steep, and nowhere are there precipices of rock to stop the climber. We now know that it can be reached, by means of a subsidiary ridge, from a col 23,000 feet, the Chang La, that lies to the north of the North-east arête. This col was the highest point on Mount Everest reached by the Expedition, and had it not been for savage weather a considerably higher altitude would have been attained; for above the col for several thousand feet lay an unbroken snow-slope.