Report of the Kew Observatory Committee. 



7 



the two portable electrometers, the ODe situated on the pillar in the 

 garden, the other at the same height on a tripod stand, at some 

 distance in the park. It is hoped that time will he found to repeat 

 the experiments on sufficiently numerous occasions to allow some 

 conclusions to be drawn. 



Aneroid Barometers. — The experiments referred to in the last three 

 " Reports " were continued in the early part of the year. The results 

 have been discussed by the Superintendent in a paper recently pub- 

 lished in the Society's * Transactions.' 



Platinum Thermometry. — The experimental work carried out at 

 the International Bureau of Weights and Measures at Sevres by 

 Dr. J. A. Harker .in co-operation with Dr. Chappuis lias only just 

 terminated. It has comprised a careful comparison of certain 

 platinum thermometers belonging to the Observatory with a gas 

 thermometer belonging to the Bureau, over the range —30° C, to 

 + 600° C. 



Dr.Harker brought back the platinum thermometers, vesistance box, 

 &c, to the Observatory late in December, and is about to be engaged 

 in preparing the results for publication. In view of this and other 

 special thermometric work in contemplation, the Committee have 

 temporarily secured the services of Dr. Harker in the capacity of 

 special assistant to the Superintendent. 



Experiments have been continued at the Observatory itself on the 

 fixity of zero, and the general behaviour of platinum thermometers, 

 which have shown, amongst other things, the expediency of carefully 

 checking the behaviour of the " leads." 



Experimental work on the comparison of platinum and mercury 

 thermometers has also been continued, and it is hoped that it will 

 shortly be possible, utilising the results of Dr. Harker's work at 

 Sevres, to issue certificates to high range mercury thermometers 

 embodying the results of direct comparison. 



Mercury Thermometry. — The experiments on thermometers of 

 different kinds of glass made by Messrs. Powell and Sons, to which 

 reference was made last year, have been continued. Further ther- 

 mometers are being made by Messrs. Powell, of a pattern suggested 

 by the Superintendent, with which it is hoped to experiment at 

 higher temperatures. 



V". Verification of Instruments. 



The subjoined is a list of the instruments examined In the year 

 1898, with the corresponding results for 1897 : — 



