KEW OBSERVATORY 163 



south. The repose produced by its complete isola- 

 tion is eminently favourable to scientific research. 

 In one of the lower rooms a set of self-recording 

 magnetographs, described in the Report of the last 

 meeting of the Association, is constantly at work. 

 These instruments, by the aid of photography, 

 furnish a continuous record of the changes which 

 take place in the three magnetic elements, viz. the 

 declination, the horizontal force, and the vertical 

 force. The light used is that of gas, in order to 

 obtain which, pipes have been carried across the Park 

 to the Observatory, at an expense of 250, which 

 sum was generously defrayed by a grant from the 

 Royal Society. 



6 Attached to this room is another, of a smaller 

 size, in which the necessary photographic operations 

 connected with magnetography are conducted. 



6 In the storey above the basement, the room 

 by which the visitor enters the observatory is filled 

 with apparatus. Much of this is the property of the 

 Royal Society, and some of the instruments possess 

 a historical value ; for instance, the air-pump used 

 by Boyle and the convertible pendulum designed 

 by Captain Kater, and employed by him, and sub- 

 sequently by General Sabine, in determining the 

 length of the pendulum vibrating seconds. 



' An inner room, which opens from this one, is 

 used as a library and sitting-room, and in it the 

 calculations connected with the work of the observa- 

 tory are performed. In this room dipping-needles 

 and magnets, which it is necessary to preserve from 

 rust, are stored. Here also the MS. of the British 

 Association Catalogue of Stars is preserved. 



' A room to the east of this contains the stan- 

 dard barometers, and the apparatus (described by 



