96 



Report of the Kew Committee. 



With a view of facilitating the examination of the dark glasses and 

 mirrors of sextants, of which a large number are now tested and 

 marked for makers before mounting in frames, the Superintendent 

 has devised a special apparatus for the purpose, an illustrated 

 description of which appeared in the " Proceedings of the Royal 

 Society" (vol. 35, p. 42). 



Redeterminations have been made of the angles between the 

 collimators of the Cooke sextant apparatus, which show that they 

 retain their positions with a satisfactory degree of constancy. 



The Committee have been offered the loan of the apparatus 

 employed by Mr. J. M. Crafts, of Paris, for the comparison of 

 mercurial thermometers at high temperatures, but have not yet been 

 able to avail themselves of his offer. 



Standard Barometers. — From time to time comparisons have been 

 made between the two Welsh Standard Barometers and Newman 

 No. 34, the working Standard of the Observatory, and their relative 

 values have been found to remain unchanged. 



Mr. F. Waldo, of the United States Signal Department, being 

 instructed by Major- General W. B. Hazen, Chief Signal Officer, 

 United States of America, to compare the Standard Barometers of their 

 Department with the European Standards, visited the Observatory in 

 July, and made a lengthened comparison of two Standards by Fuess, 

 which he brought with him, with the Observatory Working Standard, 

 Newman No. 34. The results of his comparison have not yet been 

 communicated to the Committee, but Dr. Chistoni, of the Italian 

 Meteorological Service, having published in the " Annale della Meteo- 

 rologia" an account of the results of his comparisons of Kew and 

 other Standard Barometers, the Committee desire to publish an 

 abstract of that part of his paper which more especially refers to the 

 Observatory Standard. 



Taking the absolute standard barometer of St. Petersburg as the 

 basis for his comparisons, Dr. Chistoni finds that the corrections of the 

 Continental standards, referred to this instrument, are as follows : — 



Barometer. 



Millim. 



In. 



» No. 5 



-0 



•35 



-0-014 



-0 



•14 



-0-006 



» No. 10.... 



-0 



•22 



-0 -009 





-1 



•16 



-0-046 





-0 



11 



-0 004 



-0 



22 



-0-009 



Stockholm, Pistor and Martins, No. 579 . . . 







00 



o-ooo 





-0 



17 



-0-007 



His first comparison with the Kew Standard was an indirect one, 



