Report of the Kew Committee. 



93 



Two of the cameras, with their tripod stands, have been received at 

 the Observatory, a base line of 180 yards has been marked off on the 

 level path leading across the park from the Observatory, and a 

 carriage for conveying the battery and reels of wire constructed. 



A. code of signals has been arranged to enable the observers at the 

 cameras to work in accordance with each other, and several successful 

 pairs of cloud negatives have been obtained, both on the plates pre- 

 pared by Captain Abney and also on gelafcino-bromide paper. 



No steps have yet been taken towards the permanent installation of 

 the apparatus at the Observatory. 



Water Surface Temperature. — The observations of the maximum and 

 minimum temperature of the surface water of the pond which were 

 taken for the late Mr. Greaves, C.E., daily at 9 a.m., were discontinued 

 at his request on May 1, and the results forwarded to him. 



Mr. Greaves applied to the Committee for permission to excavate a 

 tank in the ground attached to the Observatory, in order that con- 

 tinuous registration of water surface temperature might proceed in 

 the immediate neighbourhood of the thermograph. The Committee, 

 however, were unable to afford him the facilities he desired, the time 

 of the Observatory staff being fully occupied with their existing 

 duties. 



Nocturnal Radiation. — The experiments on the fall of temperature 

 of the lower layers of the atmosphere at sunset, instituted at the 

 suggestion of Professor Tyndall, were terminated on February 16, on 

 the resignation of the assistant by whom the readings of the thermo- 

 meters were made, the grant devoted by the Meteorological Council to 

 the purpose being almost expended. 



Graphic Reductions. — The Superintendent, having made some expe- 

 riments on the deduction of mean values, &c.,from curves by a graphic 

 method, based on Mr. Galton's composite portraiture, has communi- 

 cated a paper on the subject to the Royal Meteorological Society, 

 which has been published in the " Quarterly Journal," vol. ix. 



Artificial Horizon. — Some experiments have been made with a view 

 of testing an attachment to sextants answering the purpose of an 

 artificial horizon, which has been invented by Mr. T. Tennent, of San 

 Francisco, and constructed by Messrs. Elliott Brothers. The results 

 appear to indicate that the invention will prove a useful addition to a 

 sextant under certain conditions. 



Watch-rating. — The Committee, having decided to make a trial of a 

 system of watch-rating for the public, have granted £100 for the 

 preliminary expenses. In accordance with a scheme prepared by 

 the Superintendent, they have fitted up at the Observatory a first- 

 class burglar- and fire-proof safe for the safe custody of the watches, 

 and with a view to the obtaining of star-transits, have permitted 

 Mr. Whipple to fit up a temporary transit-house at his residence in the 



