ON COMPARING AND REDUCING MAGNETIC OBSERVATIONS. 67 
g. Slight auroral displays in Canada generally produce a marked effect 
at Toronto, but none at Greenwich. 
h. It is not easy to answer the question whether a state of disturbance 
succeeding one of calm begins or ends at the same time at both stations, 
neither beginning or ending being, in general, sufficiently definitely 
marked. 
zi. It appears impossible to assign a value based on angular movement 
alone which will be a valid test, whether such movement is due to dis- 
turbing causes or not. 
j- Angular movements at Toronto appear to be larger than at Green- 
wich, the magnets being (in 1849-50) similar—namely, 2 feet in length. 
The second research is by the Rev. 8. J. Perry and Professor Stewart, 
who, with the sanction of the Kew Committee, are engaged in a com- 
parison of the simultaneous disturbances of the declination at Stonyhurst 
and at Kew. Calling the first S, and the second K, they have obtained 
the following preliminary results, which may, however, ultimately require 
some modification :— 
S 
1) Sis always greater than K, or the ratio = is always greater than 
yss Ke ys § 
unity. 
(2) This ratio appears to depend in some way on the duration of the 
disturbance. 
(3) But not, as far as can be seen at present, upon its magnitude. 
A third research is by Professor Stewart and Mr. W. Lant Carpenter, 
who are making a preliminary trial of four years of Kew declination dis- 
turbances (separated by Sabine’s method), in order to ascertain whether 
the aggregate daily disturbance depends upon the relative position of the 
sun and moon, and also whether it is affected by meteorological storms. 
The following provisional result has been obtained from the years 1870-73 
A which the lunation is divided into 8 parts, (0) denoting new, and (4) 
ull moon. 
Mean Daily Aggregate of Disturbance of Declination at Kew.' 
(Unit +},th of an inch, measured on the curve.) 
OD) bel athicl2)o7 i) B)enoe Aded peri (Es +0 CO 
MAA deified!) 9 A045. 95, oe 8B Yr 94,0107 > 710K 
The Committee desire to draw the attention of magneticians to the 
urgent need of obtaining more accurate knowledge than we possess at 
present of the daily variation of the vertical force. No attempt to fix 
the cause of the daily variation can be made until the daily variation of 
each component of the magnetic force is known. 
In conclusion, the Committee desire their reappointment, with the 
addition to their number of Captain Creak and of Mr. G. M. Whipple, 
Director of the Kew Observatory, and they would request that the sum 
of 501. should be placed at their disposal, to be spent as they may think 
best on the researches mentioned in this report. 
1 The late Professor J. Clerk Maxwell was, it is believed, the first to suggest that 
the lunar-diurnal variation of the earth’s magnetism may be caused by distortion, and 
Dr. Schuster has suggested that, if there is found to be a relation between magnetic 
disturbances and atmospheric storms, it may be of the same nature. 
F2 
