342 



Beport of the Keio Observatory Committee. 



In the case of the Vertical Force instrument it was found necessary 

 to re-adjust the magnet, and at the same time its sensibility was 

 slightly altered, after which the scale value was again determined 

 with the following result : — 



Balance, January 26th, 1899, for 1 cm. SY == 0'00049. 



"With regard to magnetic disturbances, no very large movements 

 have been registered during the year. Some of the principal oscilla- 

 tions recorded took place on the following dates : — 



January 28—29; February 12; March 10, 22, and 23; 

 April 18—19; May 3—5; June 27—29; 

 September 26—27; and October 23. 



The hourly means and diurnal inequalities of the magnetic elements 

 for 1899, for the quiet days selected by the Astronomer Eoyal, will be 

 found in Appendix I. A correction has been applied for the diurnal 

 variation of temperature, use being made of the records from a Eichard 

 thermograph as well as of the eye observations of a thermometer 

 placed under the Vertical Force shade. 



The mean values at the noons preceding and succeeding the selected 

 quiet days are also given, but these of course are not employed in 

 calculating the daily means or inequalities. 



The following are the mean results for the entire year : — 



Mean Westerly Declination 16° 57'* 1. 



Mean Horizontal Force 0*18393 C.G.S. unit. 



Mean Inclination 67° 14'-7. 



Mean Vertical Force 0-43852 C.G S. unit. 



In September, in consequence of an accident, the two dip needles 

 long in use had to be replaced by two others obtained from Mr. A. W. 

 Dover in 1897. As a careful comparison of the data obtained before 

 and after the accident showed that the difference of the inclinations 

 given by the new and old needles if existent was less than the pro- 

 bable error of observation, no correction has been applied. 



Observations of Absolute Declination, Horizontal Intensity, and 

 Inclination have been made weekly, as a rule. 



A table of recent values of the magnetic elements at the Observa- 

 tories whose publications are received at Kew will be found in 

 Appendix Ia. 



A course of practical instruction in the taking of magnetic obser- 

 vations has been given to Mr. Henkel, of Markree Observatory, and 

 to Lieutenants Nares and Waugh, of the Eoyal Navy. The method of 

 reducing the vertical force curves has been explained to Mr. Kitto, 

 Superintendent of Falmouth Observatory. 



Captain Creak, E.N., made some preliminary experiments with a 

 modified form of Fox Circle, and Captain Denholm Fraser, E.E., 



