116 
COLONEL SABINE ON PERIODICAL LAWS DISCOVERABLE 
The variation in the amount of disturbance in the different years presented in this 
Table, has certainly far more the aspect of a periodical inequality, than of what may 
be called for distinction’s sake, accidental variation. The character, with the single 
exception already noticed, is that of an increase systematically progressive between 
the years 1843 and 1848. But the existence of a periodical inequality of this nature, 
affecting at the same time, and in the same manner, parts of the globe most remote 
from each other, would be a circumstance of such extreme importance in theoretical 
respects, that we are bound to receive the facts which may appear to indicate it with 
the utmost caution, and to await the confirmation it may obtain from contempora- 
neous observations at other stations. The magnetic disturbances present as well- 
marked and as notable features over the greater part of Europe as they do at 
Toronto and Hobarton ; and there exist, or there should exist at those European 
observatories which have professed to adopt and carry out the system of observation 
proposed by the Royal Society, hourly or two-hourly observations, not only contem- 
poraneous but simultaneous with those which have been discussed in this paper, and 
which, if examined, should yield corresponding conclusions, if the phenomena be 
general. In rnagnetical no less than in astronomical observations, the work of an 
observatory is but partially performed, until the observations have been subjected to 
processes of reduction, and their bearing on the points of theory for which they 
were instituted has been examined and shown. 
Pending such confirmation, the general progressive increase in the amount of 
disturbance at Toronto and Hobarton, between the years 1843 and 1848, derives 
great additional interest and importance from its apparent connection with an 
equally remarkable progressive increase which took place at the same two stations, 
in the magnitude of the diurnal range of the Declination in the same years. The 
Tables in which the hourly observations at Toronto and Hobarton are recorded in 
the volumes of those observatories, exhibit for each month the mean monthly diurnal 
variation ; the extreme east and west positions of the magnet at any two hours in 
these monthly means, show the mean magnitude or average range of the diurnal 
variation in that month. The subjoined Tables XV. and XVI. contain the mean 
magnitudes or ranges in the four months constituting the respective seasons, and in 
the twelve months constituting the year, in each year from 1843 to 1848. 
Table XV. — Mean monthly diurnal range of the Declination at Toronto. 
Years. 
Winter. 
Spring and Autumn. 
Summer. 
Mean in the 
whole yeai'. 
November, December, 
January, February. 
Marcb, April, 
September, October. 
May, June, 
July, August. 
1843 
5-64 
9-36 
11-70 
8-90 
1844 
5-70 
8-74 
12-17 
8-87 
1845 
5-73 
9-15 
13-36 
9-41 
1846 
6-33 
9-21 
12-27 
9-27 
1847 
7-28 
10-08 
13-84 
10-40 
1848 
9*48 
11-04 
15-82 
12-11 
