388 



Report of the Kew Observatory Committee. 



would seem important in many cases, e.g., in observations on earth 

 temperatures. 



Taking the above facts into consideration, the Committee decided 

 to instal platinum thermometers at Kew, and to institute an in- 

 dependent series of experiments into their behaviour. Attention 

 will in the first instance be directed more especially to the question 

 of the fixity of the zero and of the fundamental interval. A grant 

 of £100 was obtained from the Government Grant Committee r 

 for the purchase of platinum thermometers, and the other necessary 

 apparatus. A new room has been built for the purpose of the 

 inquiry, from designs by Mr. W. N. Shaw and Mr. E. H. Griffiths, at 

 a cost of over £120. Mr. Griffiths also kindly superintended the 

 construction of the apparatus by the Cambridge Scientific Instru- 

 ment Company, and along with Mr. C. T. Heycock he visited the 

 Observatory for some days in October, and illustrated the use of the 

 platinum thermometers, and the reduction of the observations. A 

 full account of the apparatus has been given by Mr. Griffiths in 

 4 Nature/ November 14th, 1895. 



Hitherto at Kew the examination of mercury thermometers at 

 temperatures above 100° C. has been limited to calibration. This 

 supplies trustworthy knowledge as to the uniformity of the bore and 

 the graduations, but throws no light on the suitability of the glass 

 for exposure to high temperatures. It is also inapplicable to those 

 high range thermometers in which there is gas, at high pressure, 

 above the mercury column. The Committee hope that means will 

 shortly be devised for direct comparison of thermometers at high 

 temperatures, and expect that the platinum thermometers will in- 

 cidentally prove useful for this purpose. 



V. Verification of Instruments. 



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

 1895, with the corresponding results for 1894 : — 



