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TRANSACTIONS OF SECTION E. Tits 
season when the atmosphere was most favourable for the observations, though the 
physical difficulties were not so great as in the hill tracts just mentioned, and 
labour was more easily procurable. Lying on the British frontier, at the northern 
extremities of no less than ten of the meridional chains of triangles, it had neces- 
sarily to be operated in to some extent, and Everest wished to carry the several 
chains across it, on to the outer Himalayan range, and then to connect them 
together by a longitudinal chain running along the range from east to west, com- 
pleting the gridiron in this quarter. But the range was a portion of the Nepalese 
territories, and all Europeans—excepting those attached to the British embassy at 
Khatmandu—were debarred from entering any part of Nepal, by treaty with the 
British Government. Everest hoped that the rulers of Nepal might make an ex- 
ception in his favour for the prosecution of a scientific survey ; and when he found 
they would not, he urged the Government to compel them to give his surveyors 
access, at least, to their outlying hills; but he urged in vain, for the Government 
would not run the risk of embarking in a war with Nepal for purely scientific interests. 
Thus the connecting chain of triangles—now known as the N.E. Longitudinal Series 
—had to be carried through the whole length of the Terai, a distance of about 500 
miles, which involved the construction of over 100 towers—raised to a height of 
about 30 feet to overlook the earth’s curvature—and the clearance of about 2,000 
miles of line through forest and jungle to render the towers mutually visible. It 
required no small courage on Everest’s part to plunge his surveyors into this region ; 
he endeavoured to minimise the risks as much as possible by taking up the longi- 
tudinal chain in sections, bit by bit, on the completion of the successive meridional 
chains, and thus apportioning it between several survey parties, each operating in 
the Terai for a short time, instead of assigning it to a single party to execute con- 
tinuously from end to end, as all the other chains of triangles. But notwithstand- 
ing these precautions, the peril was great, and the mortality among both officers 
and men was very considerable; greater than in many a famous battle, says Mr. 
Clements Markham, in an eloquent passage in his Memoir of the Indian Surveys, 
in which he claims for the surveyors who were employed on these operations—with 
no hope of reward other than the favourable notice of their immediate chief and 
colleagues—merit for more perilous and honourable achievement than much of the 
a service which is plentifully rewarded by the praises of men and prizes of 
a 8. 
Everest retired in 1848, and was succeeded by Waugh, who applied himself 
energetically to the completion of the several chains of triangles exterior to the 
Great Arc, for which he obtained a substantial addition to the existing equipment 
of great theodolites. It was under him that the formidable longitudinal series 
through the Terai, which had been begun by Everest, was chiefly carriedout. He 
personally initiated the determination of the positions and heights of the principal 
snow peaks of the Himalayan ranges; and he did much for the advancement of the 
general topography of India, which had somewhat languished under his predecessor, 
who had devoted himself chiefly to the geodetic operations. He retired in 1861, 
and I succeeded to the charge of the Great Trigonometrical Survey. The last 
chain of the principal triangulation was completed in 1882, shortly before my own 
retirement. 
Of the general character of the operations, it may be asserted without hesitation 
that a decree of accuracy and precision has been attained which has been reached 
by few and surpassed by none of the great national surveys carried out in other 
parts of the world, and which leaves nothing to be desired even for the require- 
ments of geodesy ; a very considerable majority of the principal angles have been 
measured with the great 24-inch and 36-inch theodolite, and their theoretical pro- 
bable error averages about a quarter of a second; of the linear measurements the 
probable error, so far as calculable, may be taken as not exceeding the two- 
millionth part of any measured Jength. And as regards the extent of the triangulation, 
if we ignore the primary network in Southern India, and all secondary triangula- 
tion, however valuable for geographical purposes, we still have a number of prin- 
cipal chains—meridional, longitudinal, and oblique—of which the aggregate length 
is 17,300 miles, which contain 9,280 first-class angles all observed, and rest on eleven 
