484
THE INDIAN EMPIRE
[CHAP.
the immediate control of the Governor-General, and the records
and plans were removed from Madras to Calcutta. Colonel
Lambton died in 1823, aged sixty-seven, at Hinganghat, 5 miles
from Nagpur, engaged to the last on the prosecution of the great
work he had initiated. His death marks the close of the first
period of the Trigonometrical Survey, as his work has little in
common with subsequent operations. For geodetic purposes
it has shared the fate of similar contemporaneous operations
in Europe, since all the measurements have had to be revised
as instruments and methods improved; but for geographical
requirements, as bases for topographical and other surveys, it is
still, and will remain, most valuable.
Develop- Lambton was succeeded in the charge of the Great Trigono-
ment by metrical Survey by Captain (afterwards Sir) George Everest of
Sir G.
Everest, the Bengal Artillery. In 1830 Captain Everest, who had
spent five years in England studying the best methods of
prosecuting the survey, returned to India, bringing with him
new instruments of the latest pattern and Colby compensation
bars for the measurement of base-lines. The greater portion
of the principal triangulation in India proper has been carried
out with the 36-inch and 24-inch theodolites then procured,
and the ten verificatory base-lines have been measured with the
Colby apparatus. Lambton had proposed to cover India with
a network of triangulation, utilizing the Great Arc Series for
geodetic measurements, but Everest, in 1830, recommended
the substitution of the 'gridiron' system. This, briefly, con-
sists of meridional and longitudinal chains of triangles, the
former at intervals of one degree apart, the latter following the
parallels of Calcutta, Bombay, and Madras across India. The
external chains or series were to follow the coast-line and the
British frontiers. The whole of this triangulation in India
proper rests on ten base-lines, of which five are in the Great
Arc Series and the others at Karachi, Attock, Sonakhoda
(near Jalpaiguri), Calcutta, and Vizagapatam. The standards
of length with which the Colby bars were compared during the
measurement of the base-lines, were two Io-feet iron standards,
a standard steel foot, and two 6-inch brass scales. One of
these iron standards was employed at the measurement of all
ten base-lines between 1832 and 1869, while the other has
been compared with the Ordnance Survey standard in England
and with several continental standards of length. Everest's
programme of operations, based on the 'gridiron' system,
received the approval of the Government of India and the
Court of Directors, and its main principles have been followed
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