Report of Magneticcd Observations at Falmouth Observatory, 41 5 



Beport of Magnetical Observations at Falmouth Observatory for 

 the Year 1900. Latitude 50° 9' 0" N., Longitude 5° 4' 35" W. : 

 height, 167 feet above mean sea-level. 



The Declination and the Horizontal Force are deduced from hourly 

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

 diurnal variation. 



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 and vibration. These were made with the 

 Collimator Magnet, marked 66a, and the Declinometer Magnet, marked 

 66c, in the Unifilar Magnetometer No. 66, by Elliott Brothers, of 

 London. The temperature correction (which is probably very small) 

 has not been applied. 



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

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

 tions and for any disturbance. V is the product of H and of the 

 tangent of the Observed Dip (uncorrected likewise for diurnal 

 variation). 



In Table VI the Inclination is the mean of the absolute observations, 

 the mean time of which is 3 p.m. The Inclination was observed with 

 the Inclinometer No. 86, by Dover, of Charlton, Kent, and needles 1 

 and 2, which are 3 J inches in length. 



The Declination and the Horizontal Force values given in Tables I to 

 IV are prepared in accordance with the suggestions made in the Fifth 

 Beport of the Committee of the British Association on comparing and 

 reducing magnetic observations, and the time given is Greenwich Mean 

 Time, which is 20 minutes 18 seconds earlier than local time. 



The following is a list of the days during the year 1900 which were 

 selected by the Astronomer Boyal as suitable for the determination of 

 the magnetic diurnal variations, and which have been employed in the 

 preparation of the magnetic tables : — 



January ... 3, 8, 9, 30, 31. 

 March ... 5, 11, 21, 27, 28. 

 May ... 9, 10, 14, 21, 28. 

 July ... 14, 15, 18, 22, 30. 

 September 2, 7, 21, 25, 26. 

 November 5, 6, 11, 16, 30. 



February ... 3, 6, 7, 13, 28. 



April 3, 8, 15, 22, 25. 



June 10, 11, 16, 20, 25. 



August ... 6, 9, 10, 23, 30. 

 October ... 2, 7, 13, 19, 31. 

 December 3, 6, 15, 23, 24. 



EDWABD KITTO, 



Magnetic Observer. 



