6 



Report of the Kew Observatory Committee. 



of the boom, -winch, is still too liable to get off its pivot ; but the 

 record has been, on the whole, satisfactory for the latter half of the 

 year. The following table gives particulars respecting the time of 

 occurrence and amplitude in seconds of arc of the largest movements 

 actually recorded : — 





Time (Q-.M.T.). 



Amplitude. 



Date. 



h. 



m. 





// 





7* 



19-8 p.m. 



£i • ) 







21-8 



J5 



3*4 







26-7 



JJ 



3-0 



■>■> • 



. . . . . ,, 



31*4 



JJ 



2-2 





. . . 8 



34-9 



?? 



2-7 







37-0 



?) 



1-5 







37-8 



J? 



1-7 







40-7 





1-6 





.... 1 



443 



55 



0-5 







46-4 



5? 



0-6 







58-6 



5> 



06 



The times deduced for the commencement of the above-mentioned 

 earthquakes were 6 h. 47*6 m., 8 h. 4*5 m., and 1 h. 37 m. re- 

 spectively. 



Without special very careful experiments it would be difficult to 

 say what is the probable error in fixing the precise times. Inde- 

 pendent measurements of the photographic trace may agree to O'l or 

 0'2 of a minute, but there is room for a certain amount of doubt as to 

 the proper values to attribute to the time marks on the sheet. 



In the case of the times of commencement of a disturbance the 

 uncertainty is greater, because the movement may be initially infini- 

 tesimal, and because a tiny movement arising from a different source 

 (such movements being not uncommon) might intervene. 



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, referred to in last year's Report, 

 have been contir.ued, and the observations have been taken twice 

 every month. 



During October some simultaneous observations were made with 



