Description of the Kew Observatory. 139 



Wheatstone. The staff employed at the Observatory has increased 

 from eight in 1871 to fifteen in 1896. 



The chief executive officer under the Committee is styled " Super- 

 intendent," the present occupant of the post being Dr. C. Chree. 

 The previous superintendents under the Royal Society's Committee 

 were Mr. S. Jeffery, 1871-76, and Mr. G. M. Whipple, 1876-93. 

 Amongst those who held the post prior to 1871 maybe mentioned Sir 

 Francis Ronalds, Mr. John Welsh, and Prof. Balfour Stewart. In 

 addition to the general management of the Observatory, the duties of 

 the Superintendent include the response to inquiries on various 

 scientific matters from Government Departments, especially the 

 Meteorological Office, as well as from individuals engaged in scien- 

 tific pursuits. 



The relations between the Observatory and the Meteorological 

 Office have been very close ever since 1867, as the Observatory has 

 since that date acted as the central observing station for that Office. 



DESCRIPTION OF OBSERVATORY. 

 BASEMENT (see plan No. I). 



Magnetograph Room. This room contains the Magnetographs (1), 

 which were erected in their present form by Mr. Welsh in 1856. 

 The instruments show variations in the Declination, Horizontal 

 Force Component, and Vertical Force Component. Light from fixed 

 gas jets is reflected from mirrors attached to the magnets on to 

 photographic paper. The paper is wound round drums driven by 

 clock-work, and thus a continuous record is obtained of variations 

 either in the direction or intensity of the earth's magnetic force 

 (<B.A. Report,' 1859, pp. 200228). 



The magnetograph curves are standardised by means of direct 

 observations on the strength of the magnets, made from time to 

 time, and the employment of the results of the absolute observations, 

 carried out weekly in a wooden hut (1, Plan II) situated in the 

 garden. 



The Barograph (2) is a modified form of that originally designed 

 by Ronalds. A beam of light passes through the chink left between 

 a horizontal stop and the surface of the mercury in the tube of a 

 barometer, and falls upon photographic paper. When the mercury 

 rises in the barometer tube, the beam of light is narrowed, and the 

 trace correspondingly reduced in width, the reverse happening, of 

 course, when the mercury falls (' Report of the Meteorological Com- 

 mittee,' 1867, p. 40). 



Photographic Eoom. This immediately adjoins the magnetograph 

 room, see Plan I. 



