370 
COLONEL SABINE ON PERIODICAL LAWS DISCOVERABLE 
and very naturally imagined that the early hours of the night, or from 8 p.m. to 
11 P.M., are those at which magnetic disturbances principally take place; that 
about 11 P.M,, or a little after, they begin to subside, disappearing almost wholly 
in the day-time, and reappearing again possibly the following evening at the same 
hour as on the preceding evening, in supposed analogy with certain atmospheric 
disturbances which manifest a tendency to recur at the same hours on successive 
days. It is in this supposed analogy that the term of magnetic storms appears to 
have originated. An examination of the observations of the three elements at but a 
single station (as Toronto for example), teaches us that this view requires to be con- 
siderably modified. The disturbances of the Declination which reach a maximum at 
9 P.M. have indeed already subsided considerably at 11 p.m. ; but those of the Inclina- 
tion show no abatement until about 2 a.m. ; whilst those of the Total Force, which are 
much below their average value at 9 p.m., increase progressively to their maximum, 
which is only reached at 3 a.m., or nearly six hours after the maximum of the Declina- 
tion-disturbances has taken place. In like manner, the hours of the afternoon in 
which the Declination is but little disturbed, and which have been supposed in con- 
sequence to be hours in which an intermission of disturbance takes place, are seen 
by the Table to be precisely those hours at which the disturbances which increase the 
Total Force have their principal development, being then in the proportion of nearly 
ten to one when compared with the homonymous hours after midnight. When these 
remarkable phenomena are more fully studied, the aspect they present is that of a 
disturbance continuing frequently through several successive days, changing from 
one element to another, and affecting each at different hours and in different modes, 
in conformity with laws, the average operation of which it has been the object of this 
investigation to ascertain ; and wearing the appearance consequently, when only a 
single element is regarded, of a limitation to those hours when that element in par- 
ticular is affected, but which appearance ceases when the phenomena are more 
generally apprehended. It was the supposed analogy between magnetical and atmo- 
spherical disturbances, which led, in the commencement of the British Colonial 
Observatories, to the simultaneous observations and record of these two great, and, 
as we have now reason to believe, distinct branches of natural phenomena; and as 
the inquiry advances, we are continually becoming acquainted with additional cir- 
cumstances to strengthen the persuasion, that the causes of these occasional and 
previously supposed “ irregular” manifestations of disturbing magnetical influence 
must be sought in a more distant source than in variations of the meteorological 
phenomena. 
There is another misapprehension in regard to the nature of the occasional 
disturbances which has followed very naturally from the limitation of the view to 
the disturbances of a single element; an inference has sometimes been drawn in 
favour of a local origin of a particular disturbance (in contradistinction to the general 
fact of their simultaneous occurrence at extremely distant parts of the globe) from 
