416 



Beporf of Magnetical Observations at 



The Declination and Horizontal Force are deduced from hourly 

 readings of the photographic curves, and so are corrected for the 

 diurnal variation. 



The Inclination is the mean of the absolute observations, the mean 

 time of which is 3 P.M. 



In Table V, X is the mean of the absolute values observed during 

 the month (generally three in number), uncorrected for diurnal 

 variations and for any disturbance. Y is the mean of the products of 

 the Dips and the X. 



The results in the following tables, Nos. I, II, III, IV, are deduced 

 from the magnetograph curves which have been standardised by 

 observations of deflection arid vibration. These were made with 

 the Collimator Magnet marked 66a, and the Declinometer Magnet 

 marked 66c in the Unifilar Magnetometer by Elliott Brothers, of 

 London. Table No. V is deduced from these observations. The 

 temperature correction (which is probably very small) has not been 

 applied. 



The Inclination was observed with the Inclinometer No. 86, by 

 Dover, of Charlton, Kent, and needles 1 and 2, which are 3 \ ins. 

 in length, the results of which appear in Table VI. 



The Declination and Horizontal Force values given in Tables I to 

 IV are prepared in accordance with the suggestions made iu the 

 fifth report of the Committee of the British Association on com- 

 paring and reducing magnetic observations, and the time given is 

 Greenwich mean time, which is 20 min. 18 sec. earlier than local time. 



The following is a list of the days during the year 1895 which 

 were selected by the Astronomer Royal, as suitable for the deter- 

 mination of the magnetic diurnal variations, and which have been 

 employed in the preparation of the magnetic tables : — 



January 5, 13, 25, 26, 27. 



February ... ..... 4, 13, 22, 25, 26. 



March 7. 11, 12, 24, 27. 



April ,,„;,. 2, 8, 21, 22, 29. 



May ........ 4, 12, 16, 19, 23. 



June 6 ... 8, 13, 14, 15, 26 



July 3 5 7, 19, 24, 25 



August 2, 3, 7, 22, 27. 



September 2, 7, 8, 21, 28 



October 3, 10, 18, 21, 22 



November 7, 14, 17, 19, 21. 



December 4, 5, 6, 16, 29, 



The Azimuth of the fixed mark used in deducing the Observations 

 of Absolute Declination was checked by Professor A. W. Riicker, 

 M.A., F.R.S., on August 7, 1895, by means of an Observation of the 



