Report of the Kew Committee, 



475 



I. Magnetic Observations. 



No change has been made in the magnetographs during the past 

 year. The curves representing Declination, Horizontal Force, and 

 Vertical Force variations have been obtained uninterruptedly, and, 

 as in former years, the scale values of all the instruments were 

 determined in the month of January. 



The ordinates of the various photographic curves were then ascer- 

 tained to be as follows : — 



Declination : 1 inch=0° 22''04. 1 cm.=0° 8'7. 



Bifilar, January 15, 1889, for 1 inch BB. - O0278 foot grain unit. 



„ 1cm. „ = 0-00050 C.G.S. unit. 

 Balance, January 16, 1889 „ 1 inch £V= 0'0285 foot grain unit. 



„ 1 cm. „ = 0-00052 C.G.S. unit. 



The principal magnetic disturbance of the year was recorded on 

 the morning of July 16th; on July 11th between 10 and 11 p.m. the 

 curves registered the passage of tremors from an earthquake which 

 was experienced in Central Asia. 



Observations with the absolute instruments have been made 

 monthly, and the results are given in the tables forming Appendix I 

 of this Heport. 



The magnetic instruments have been studied, and a knowledge of 

 their manipulation obtained, by Lieutenant W. J. Combe, of 

 H.M.S. "Penguin." 



With a view of ensuring accuracy in the tables employed in the 

 reduction of magnetic observations, which have been frequently 

 reprinted for use by observers, a careful examination has been made 

 by Professor G. Carey Foster of all the formulas and blank forms 

 employed in the Kew methods. He has reported to the Committee 

 that he did not detect any inaccuracy. 



A careful examination of the observations of Absolute Declination 

 made at Kew from 1858 to the present date has been made at the 

 request of Professors Thorpe and Rucker, who have been inves- 

 tigating the secular changes of Declination during the interval. 

 The results have been forwarded to those gentlemen with the object 

 of their embodiment in the paper on the Magnetic Survey of the 

 British Islands now in progress submitted by them to the Royal 

 Society. 



In order to examine certain features of the working of the Kew 

 pattern Vertical Force magnetograph instrument, Mr. Charles 

 Chambers, F.B.S., Director of the Colaba Observatory, Bombay, has 

 been provided by the Indian Government with a new instrument of 

 the same pattern, which has been tested at Kew, and forwarded by 

 the maker, Adie, to Bombay. 



