however, there are, as Sir Sidney Burrard has pointed out in his discussion of this point in Burrard and Hayden's Himalaya and Tibet, many causes of slight error in observing and computing the altitude of a distant and very lofty peak. The observations are made with a theodolite. The telescope of the theodolite may not be absolutely perfect. The theodolite may not be levelled with perfect accuracy. The graduations on the circle of the theodolite may not be quite accurate. The observer himself may not have observed with sufficient perfection. An error of ten feet may have resulted from these causes. Then there are other and greater sources of possible error. There may be error in the assumed height of the observing station; and the altitudes of peaks are always varying in nature with the increase and decrease of snow in summer and winter and in a season of heavy snowfall or a season of light snowfall. Another source of error arises from the varying effects of gravitational attraction. “The attraction of the great mass of the Himalaya and Tibet,” says Burrard, “pulls all liquids towards itself, as the moon attracts the ocean and the surface of the water assumes an irregular form at the foot of the Himalaya. If the ocean were to overflow Northern India its surface would be deformed by Himalayan attraction. The liquid in levels is similarly affected and theodolites cannot consequently be adjusted; their plates when levelled are still tilted upward towards the mountains, and angles of observation are too small by the amount the horizon is inclined to the tangential plane. At Darjeeling the surface of water in repose is inclined about 35̎ to this plane, at Kurseong about 51̎, at Siliguri about 23̎, at Dehra Dun and Mussooree about 37̎. For this reason all angles of elevation to Himalayan peaks measured from the plains, as Mount Everest was measured, are too small and consequently all our values of Himalayan heights are too small. Errors of this nature range from 40 to 100 feet.”

This then is a considerable source of error, but the most serious source of uncertainty affecting the value of heights is the refraction of the atmosphere. A ray of light from a peak to an observer's eye does not travel along a straight line but assumes a curved path concave to the earth. The ray enters the observer's eye in a direction tangential to the curve at that point, and this is the direction in which the observer sees the peak. It makes the peak appear too high. Corrections have therefore to be applied. But there is no certainty as to what should be the amount of the correction; and it is now believed that the computers of the height of Mount Everest applied too great a correction for refraction and consequently reduced its height too much.

Burrard brings together in the following table the different errors to which the carefully determined height of Mount Everest is liable:—

The following table shows how the different values of the height of Mount Everest have been deduced:—

Height of Mount Everest

The height 29,141 is still, Burrard thinks, too small, as it has yet to be corrected for the deviations of gravity. But though it is a more reliable result than 29,002, the latter is still to be retained in maps and publications of the Survey of India.

As to the name, it was called Everest after the distinguished Surveyor-General of India under whose direction the triangulation had been carried out, one result of which was the discovery of the mountain. From the Indian side and Nepal it is not a conspicuous peak on account of its lying so far back. No native name for it could be discovered and Sir Andrew Waugh, the successor of Sir George Everest, called it after his predecessor. From the Tibetan side it is much more conspicuous and, as General Bruce stated in his lecture to the Royal Geographical Society in November 1920, and as Colonel Howard-Bury found in 1921, the Tibetans call it Chomolungma, which Colonel Howard-Bury translated, the “Goddess Mother of the Mountains”—a most appropriate name. But the name Mount Everest is now so firmly established throughout the world that it would be impossible to change it. It is therefore now definitely adopted.

Now, this mountain so coveted by mountaineers is unfortunately situated exactly on the border between two of the most secluded countries in the world—Nepal and Tibet. To reach it the climbers must pass through one or other of these countries and the difficulty of getting the necessary permission is what has so far prevented any attempt being made to attack Mount Everest. But recently access through Tibet has become more possible, and it so happens that it is on the Tibetan side that the summit seems most