Report of the Kew Observatory Committee. 165 



mittee and other eminent astronomers on the subject, with the result 

 that they decided that the eye observations should cease at the end of 

 1897. 



IV. EXPERIMENTAL WORK. 



Fog and Mist. The observations of a series of distant objects, 

 referred to in previous Reports, have been continued. A note is taken 

 of the most distant of the selected objects which is visible at each 

 observation hour. 



Atmospheric Electricity. The comparisons of the potential, at the 

 point where the jet from the water-dropper breaks up, and at a fixed 

 station on the observatory lawn, mentioned in last year's Report, 

 have been continued, and the observations have been taken nearly 

 every month. 



A comparison of these observations with the corresponding results 

 from the electrograms encourages the belief that there has been no 

 progressive change of insulation in the electrograph, such as was met 

 with prior to the late alterations and improvements. 



Advantage was taken of the occurrence of some very thick fogs in 

 November, to carry out six sets of observations of the potential at 

 various heights from the ground to 70 feet above. 



Aneroid Barometers. The experiments referred to last year have 

 been continued, and a considerable number of interesting conclusions 

 have been arrived at. It is hoped that the results will be ready for 

 publication in the course of the present year. 



Platinum TTiermometry . In accordance with the arrangement 

 alluded to in last year's Report, Dr. J. A. Harker came to the 

 Observatory in January to do some work in platinum thermometry. 

 The authorities of the International Bureau of Weights and Measures 

 at Sevres having consented with the greatest readiness and courtesy 

 to a comparison by Dr. Harker, in their laboratories, of the scales of 

 the hydrogen and platinum thermometers, the Committee decided 

 to do all in their power to make the scheme successful. It had been 

 from the first the hope of the Committee that platinum thermometry 

 would prove a valuable auxiliary in direct comparison of mercury 

 thermometers, especially at temperatures outside the range to 

 100 C., and the opportunity of a comparison with the standard gas 

 thermometer of the Bureau International thus occurred very oppor- 

 tunely. 



After Dr. Harker's arrival at Kew it was found that somewhat 

 extensive alterations would be required to fit the existing resistance 

 box for the work at Sevres, and it also appeared undesirable that 

 the Observatory should be deprived for some months of the means of 

 using platinum thermometers. A new resistance box was accordingly 

 ordered from Messrs. Crompton & Co., embodying the alterations 



