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