Major-General Sabine on Colonial Magnetic Observatories. 805 
termine these data with a precision which is greatly in advance of 
preceding experience, and, as far as may be judged, equal to the 
present requirements of theoretical investigation. This is the more 
deserving of notice, because Toronto is a station where the casual and 
periodical variations, which it was apprehended would seriously in- 
terfere with the determination of absolute values, are unusually large. 
We may derive, therefore, from the results thus obtained, the greatest 
encouragement to persevere in a line of research which is no longer 
one of doubtful experiment, and to give it that further extension 
which the interests of science require. 
Amongst the results which have recompensed the labours of the 
Colonial Observatories in this branch’of their inquiries, perhaps there 
is none of more importance in respect to the general theory of ter- 
restrial magnetism, than the conclusion which has been established 
by means of the observations of the Declination at St. Helena, that 
the current annual amount of secular change takes place by equal 
aliquot portions in every month, and even in every fortnight of the 
year. 'The magnitude of the annual change of the Declination at 
St. Helena, 8’ (or more precisely 7':93 in each of the eight years in 
which the observations were maintained), and the comparative tran- 
quillity of the tropical regions in regard to magnetic disturbances, 
were circumstances which rendered St. Helena a particularly eligible 
locality for an investigation of this nature. The result has been, to 
remove secular change altogether from the category of atmospheric 
or thermic relations, with which, in the absence of a correct know- 
ledge of the facts, it has frequently been erroneously associated ; and 
to show conclusively that it isa phenomenon of far more systematic 
order and regularity than has been generally apprehended (Proceed- 
ings of the Royal Society, vol. vii. pp. 67-75). 
It has thus been shown, that, in each and all of the branches of 
inquiry for which the institution of the Colonial Observatories was 
recommended, they have accomplished the objects which were con- 
templated, and have in many respects exceeded the expectations on 
which their recommendation was founded. Nor has the scope of 
their performance been limited to a mere registry of the observa- 
tions, or to their publication in a crude and undigested form. It was 
well remarked by an authority of the greatest weight, when address- 
ing the British Association on the occasion of the assembly of the 
Magnetical and Meteorological Conference at Cambridge in 1845 
(Herschel, Address, p. xxxv), that “A man may as well keep a 
register of his dreams, as of the weather or any other set of daily 
phenomena, if the spirit of grouping, combining, and eliciting results 
be absent.” To advance by the simple and straightforward path of 
inductive inquiry, in a science such as terrestrial magnetism in which 
a physical theory has yet to be sought, the endeavour must be made 
‘to grapple with the palpable phenomena, seeking means to reduce 
their features to measurement; the measurements to laws; the laws 
to higher generalizations ; and so, step by step, to advance to causes 
and theories.” The mere observational part is not, and ought never 
Phil, Mag, 8, 4, Vol, 14, No, 93, Oct, 1857, 
