Such are some of the advantages which men in general will obtain from the attempt to climb Mount Everest. But it is time now to say something of the mountain itself.

Mount Everest for its size is a singularly shy and retiring mountain. It hides itself away behind other mountains. On the north side, in Tibet, it does indeed stand up proudly and alone, a true monarch among mountains. But it stands in a very sparsely inhabited part of Tibet, and very few people ever go to Tibet. From the Indian side only its tip appears among a mighty array of peaks which being nearer look higher. Consequently for a long time no one suspected Mount Everest of being the supreme mountain not only of the Himalaya but of the world. At the time when Hooker was making his Himalayan journeys—that was in 1849—Kanchenjunga was believed to be the highest.

How it was eventually discovered to be the highest is a story worth recording. In the very year that Hooker was botanising in the Sikkim Himalaya the officers of the Great Trigonometrical Survey were making observations from the plains of India to the peaks in Nepal which could be seen from there. When they could find a native name for a peak they called it by that name. But in most cases no native name was forthcoming, and in those cases a Roman number was affixed to the peak. Among these unnamed peaks to which observations to determine the altitude and position were taken from stations in the plains was Peak XV. The observations were recorded, but the resulting height was not computed till three years later, and then one day the Bengali Chief Computer rushed into the room of the Surveyor-General, Sir Andrew Waugh, breathlessly exclaiming, “Sir! I have discovered the highest mountain in the world.” The mean result of all the observations taken from the six stations from which Peak XV had been observed came to 29,002 feet, and this Peak XV is what is now known as Mount Everest.

The question is often asked, “Why twenty-nine thousand and two?” “Why be so particular about the two?” The answer is that that particular figure is the mean of many observations. But it is not infallible. It is indeed in all probability below rather than above the mark, and a later computation of the observed results puts the height at 29,141 feet. In any case, 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:—

Source of error.Magnitude of possible error.
Variation of snow level from the meanUnknown
Errors of observation10 feet
Adoption of erroneous height for observing station10 feet
Deviation of gravity60 feet, too small
Atmospheric refraction150 feet, too small

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

Height of Mount Everest

Observing station.Year of
observation.		Distance
in miles.		Height as
determined
by Waugh.		Determination
of height
with revised
correction for
refraction.
FeetFeet
Jirol184911828,99129,141
Mirzapur184910829,00529,135
Joafpati184910829,00129,117
Ladnia184910828,99829,144
Harpur184911129,02629,146
Minai185011328,99029,160
Suberkum188187—29,141
Suberkum188387—29,127
Tiger Hill1880107—29,140
Sandakphu188389—29,142
Phallut190285—29,151
Senchal1902108—29,134
Mean——29,00229,141