HEADQUARTERS OF SURVEY DEPARTMENT. 233 



run over the country to form a basis for canal, railway, and other 

 operations. Vol. I. of the general account of the operations of the 

 Great Trigonometrical Survey was completed in 1870. In 1878 and 

 1879 Volumes II., III., and IV. were produced, giving a general 

 account of the triangulation and its reduction, with full details of 

 the North- West Quadrilateral ; also Vol. V., giving an account of 

 the Pendulum Operations; this was followed in 1880 by Vol. VI. 

 for the South-East Quadrilateral, in 1882 by Volumes VII. and VIII. 

 for the North-East Quadrilateral, in 1883 and 1887 by Volumes IX. 

 and X. on the Electro-telegraphic longitude operations executed 

 during 1875-77 find 1880-84, and in "l890 by Vol. XI. on the 

 Astronomical Observations for Latitude made during the period 

 1805 to 1885, and Vols. XII. and XIII. on the southern Trigon. 

 Of the synoptical volumes — which give a precis of the results, both 

 principal and secondary, for topographical and geographical require- 

 ments — twenty -three have been published in all. 



In the volume on the Pendulum Operations it is shown that the 

 steps which had been taken to connect the Kew Observatory, 

 the base-station of the Indian operations, with the Greenwich 

 Observatory, which was an important station of the European 

 operations, had not sufficed to effect the desired connexion. The 

 absolute length of a seconds' pendulum of the Kater pattern, which 

 had been determined at Greenwich by General Sabine in 1831, was 

 determined with the same pendulum at Kew by Major Heaviside 

 in 1873, in the expectation that this would suffice for the connexion 

 of the operations at the two observatories ; but the result gave 

 three more vibrations in 24 hours at Kew than at Greenwich, which 

 was highly improbable ; as it corresponds to a change in latitude 

 of about 1°, whereas the two observatories are nearly in the same 

 latitude and only ten miles apart. Colonel Herschel was therefore 

 deputed to determine the vibration numbers at Kew and Greenwich 

 with the invariable pendulums which had been used in India. 

 He was also authorised to take the pendulum to America and swing 

 them at some of the pendulum stations of the United States Coast 

 and Geodetic Survey, with a view to a further connexion with the 

 Indian operations. He made observations accordingly, employing 

 the two Indian pendulums, and a third pendulum of the same 

 pattern which he obtained at the Kew Observatory ; he swung all 

 three pendulums at Kew and Greenwich, in London, and at 

 Washington and Hoboken in the United States. He then made over 



