236 
MAJOR-GENERAL SABINE ON THE DISTURBANCES OF THE 
of the probability of a connexion subsisting between the magnetic disturbances and the 
more general phenomena of the earth’s magnetism, with M. Gauss’s inference from 
the Gottingen researches, that the source or sources (“ point or points of apparent 
origin ”) from whence the disturbing action in the northern hemisphere proceeds must 
necessarily be sought in the north, or in the north-west, of the European continent, it 
seemed reasonable to infer hypothetically that a connexion might be found between 
the “points of origin” of the disturbances, — if these could be more precisely ascer- 
tained and their separate effects distinguished apart, — and the poles or points of the two 
magnetic systems, of which we have the resultants in the centres of the two isody- 
namic lemniscate-loops. The first analysis of the disturbances had shown the disturb- 
ances to be strictly periodical phenomena in their mean effects, and had traced them 
directly to the sun as their primary source, inasmuch as they were found to be governed 
everywhere by laws depending upon the solar hours. Those who are familiar with the 
theory by which the transmission of light from the sun to the earth is explained, will 
have little difficulty in admitting a similar explanation of the mode by which magnetic 
influences may be conveyed from the sun to the earth. The analogy has been directly 
recognized and reasoned upon in the explanation of magnetic phenomena by Professor 
Challis in recent papers. It is when the influences reach the earth that the modes of 
their reception, distribution, and transmission may be less clearly apprehended; but 
these are within our own proper terrestrial domain and sphere of research, and are 
therefore more particularly the subjects to which our investigations maybe most usefully 
directed. We have here to guide us the simple analogy of a magnetic impulse imparted 
to a bar already magnetized ; the impulse is at once distributed throughout the bar ; 
the poles or points of greatest force being affected in the greatest degree, and the effects 
diminishing as the middle of the bar is approached. We may conceive that in like 
manner a magnetic impulse communicated from without might, in either hemisphere or 
in both simultaneously, be received by and produce its principal effect on the poles or 
points of greatest force belonging to the hemisphere, either augmenting or diminishing, 
as the case maybe, the mean or ordinary magnetism of each, and thenceforward acting 
generally and conjointly throughout the hemisphere according to laws which are or may 
be capable of determination by suitable means. The possibility of tracing a certain 
locality, or localities, on the globe as a “point or points of origin” where the magnetic 
influences being received might thenceforward distribute themselves according to the 
laws of magnetic propagation, had already been entertained by M. Gauss. In the 
first analysis of the disturbances at the British Colonial Observatories, referred to in 
p. 233, those of each element were treated simply in their aggregate effects, as might 
be conceived to be suitable on the supposition of their proceeding from a single source 
only. The result was sufficient to manifest their strictly periodical character, and to 
refer them to the sun as their primary source ; but it was at the same time obvious that 
this first analysis could by no means be regarded as a final one, inasmuch as in every 
case there was exhibited a plurality of maxima and minima in the diurnal progression ; 
