History of the Kew Observatory. 



65 



up to the end of February, 1872, at which epoch the period expired 

 which was originally fixed by Mr. de la Rue for the continuance of 

 the observations at the expense of the Royal Society Government- 

 Grant Fund. The observations were afterwards carried on up to the 

 end of March, with the object of fully including ten years. Since 

 that date eye observations of the sun, after the method of Hofrath 

 Schvvabe, have been made in order that the observations for connect- 

 ing sun-spots with magnetic phenomena might not drop through until 

 photographic records had been taken up on a permanent footing. 



In order to furnish the final corrections to the reductions of the 

 sun-pictures, a scale of equal parts, 15 feet in length, designed by Mr. 

 de la Rue, and made at his expense, was, with the sanction of Her 

 Majesty's Office of Works, erected temporarily on the Pagoda at the 

 Royal Gardens, Kew. This was photographed by the Kew Photo- 

 heliograph, and so enabled the optical distortion of that instrument to 

 be determined. 



Observations were continued for several months, when the apparatus 

 was taken down, and the Photoheliograph lent for two years to the 

 Astronomer Royal for use at Greenwich. 



1873. A series of experiments were commenced and carried on for 

 a space of nearly two years at the expense of the Meteorological Com- 

 mittee, at the Pagoda in the Royal Gardens, to test the influence of 

 height above the ground on the vertical distribution of temperature. 

 The thermometers were placed at three different levels, viz., 22 feet 

 6 inches, 69 feet, and 128 feet 10 inches above the ground. 



In the month of May a request was received from Col. J. T. Walker, 

 F.R.S., Superintendent of the Great Trigonometrical Survey of India, 

 for provision to be made at the Observatory for vibrating pendulums. 



In the year 1865 two pendulums lent by the Royal Society for use 

 in India had been vibrated at Kew by the late Capt. Basevi, as explained 

 above ; and it was necessary that these pendulums should be vibrated 

 again on their return, and that at the same time two pendulums 

 obtained from the Imperial Academy of Sciences at St. Petersburg 

 should also be vibrated. 



The Committee at once complied with the request ; and at the 

 expense of the Indian Government preparation was made for the 

 experiments in the south hall on the basement story, by removing for 

 a time the apparatus for testing sextants, and building up from the 

 foundation-arches two solid isolated supports for the Russian clock 

 and pendulum. 



Capt. Heaviside, R.E., the officer charged with the duty of making 

 the pendulum experiments, arrived in England in July, and, finding 

 all the arrangements satisfactory, at once commenced his operations. 



Endeavours were made, in connection with the arrangements just 

 mentioned, to obtain an electrical time communication between Kew 



VOL. XXXIX. 



