MAGNETIC DECLINATION AT KEW AND NERTSCHINSK. 
235 
The Report anticipates, as the probable result of the researches then about to be 
instituted, the establishment of an intimate connexion between the casual and transitory 
variations and the “ general causes of terrestrial magnetism.” Whatever these may be, 
our best inferences in regard to them must be based upon the knowledge we possess of 
the actual distribution of the magnetic influence upon the surface of the globe. In 
regard to this distribution, the Report refers throughout to two works as containing the 
embodiment of the totality of the known phenomena, viz. 1, a memoir, published two 
years antecedently (1838) in the Transactions of the British Association for the Advance- 
ment of Science, entitled “ On the Variations of the Magnetic Intensity in different 
parts of the Earth’s Surface,” in which the results of recent researches in almost all the 
accessible parts of the globe were brought together and coordinated, and their bearing 
on earlier systematic views discussed; and 2, M. Gauss’s ‘ Allgemeine Theorie des 
Erdmagnetismus,’ published in 1839, being the year preceding that in which the Report 
of the Royal Society was published*. These two works are referred to throughout the 
Report as supplying, the first the observational, and the second the theoretical bases of 
the Instructions drawn up for the guidance of those who were to conduct, and of those 
who were willing to take part in the proposed magnetic researches by sea and by land. 
In both works, the facts which had been ascertained were found to be in accordance 
with (and so far confirmatory of) the theory which we owe to the combined industry 
and sagacity of our illustrious countryman and Fellow, Halley, of the existence of a 
double system of magnetic attraction on the surface of the globe, the direction and 
intensity of the magnetic force being at all points the resultant effects of the two separate 
systems. In both works, the localities to which the resultant Poles, or Points of 
greatest force (in the northern hemisphere), were traced, were nearly the same, viz. 
one in the northern part of the American continent, and the other in the northern part 
of the Europseo-Asiatic continent. To have determined their precise geographical 
positions, it would have been requisite that the observations from which they were 
derived should have corresponded, or nearly so, to one and the same epoch, inasmuch 
as one of the magnetic systems is regarded as subject to a movement of translation 
in a geographical sense, giving rise to the phenomena of secular change. But the 
approximation in the conclusions from two such extensive and laborious coordina- 
tions as those which have been named, was fully sufficient to establish that the general 
causes of terrestrial magnetism referred to must be such as would produce the pheno- 
mena of a double system. Now, combining the expectation expressed in the Report, 
magnetic elements was particularly desirable towards a revision of his theory. It appears that of the seven 
parallels of latitude which he has employed to give the basis of his numerical calculation, the most southern is 
in 20° S. latitude. Observations carried round a parallel in a high southern latitude are consequently the 
principal desideratum. This is precisely what we have reason to hope will be accomplished by the Antarctic 
Expedition.” 
* An English translation by Mrs. Sabine of M. Gauss’s “Allgemeine Theorie” was published in 1839 in 
Taylor’s Scientific Memoirs, vol. ii. Art. V. 
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