Report of the Kew Committee. 



349 



On the conclusion of these experiments, Major Herschel conveyed 

 the pendulums, clock, &c, to America, where, after making a series of 

 observations at Washington, he handed them over to the officers of 

 the United States' Coast Survey Department, in whose charge they 

 now remain. 



Actinometry . — At the request of the Meteorological Council, the 

 actinometer devised by Professor Balfour Stewart, and described in 

 the Report of the Committee on Solar Physics, 1880, Appendix H, 

 has been obtained on loan from South Kensington, and erected on a 

 suitable stand on the Observatory Lawn. Numerous observations of 

 solar radiation have been made by it during the past summer, and 

 also several comparative observations have been made with the 

 Hodgkinson's Actinometers belonging to the Royal Society and to 

 the India Office. 



At the request and cost of the Indian Government, Sergeant 

 Rowland, R.E., who has since proceeded to India with a view of 

 observing, by means of Stewart's instrument, the solar intensity at 

 Leh, for a period of three years, has received special instruction in the 

 use of these actinometers. 



The Committee have had under consideration the desirability of 

 continuing the observations on the actinic power of daylight, which 

 ceased in November, 1875, on account of the unsatisfactory per- 

 formance of the first photometer constructed. The instrument being 

 now made in the improved form suggested by Captain Abney, R.E., 

 is not liable to the derangements experienced by that formerly 

 employed. 



Mating of Chronometers and Watches. — The Superintendent having, 

 from time to time, been requested to certify as to the going of chro- 

 nometers, has been in communication with the Directors of the 

 Observatories at Bidston, Geneva, Neuchatel, and Yale, where 

 arrangements exist for the testing and rating of chronometers and 

 superior watches. 



The Committee, after receiving his reports upon the subject and 

 also a favourable expression of opinion from the British Horological 

 Institute, considered, however, that the funds at their disposal were 

 insufficient for the present to allow them to extend their operations 

 in this direction. 



Water-surface Temperature. — At the request of Mr. C. Greaves, C.E., 

 several series of observations were taken at frequent intervals during 

 last summer of the temperature of the surface of the pond, a quarter 

 of a mile distant from the Observatory. More recently a float has been 

 moored in the centre carrying maximum and minimum thermometers 

 immersed just below the water-line. This is hauled to the shore every 

 morning at 9 a.m., and the temperatures recorded. The cost of the 

 experiment is defrayed by Mr. Greaves. 



