Major-General Sabine on Colonial Magnetic Observatories. 29% 
March 5.—The Lord Wrottesley, President, in the Chair. 
The following communication was read :— 
“On what the Colonial Magnetic Observatories have accom- 
plished.” By Major-General Sabine, R.A., Treas. and V.P.R.S. 
It has been suggested to me, that a brief review of what has been 
accomplished by the Colonial Magnetic Observatories, instituted on 
the joint recommendation of the Royal Society and British Associa- 
tion, would be acceptable; and that the officer who has been en- 
trusted with the superintendence of these establishments is the person 
from whom such a review may most properly be expected. Full 
assenting to both propositions, I have readily undertaken the task ; 
and have availed myself of the occasion to add a few remarks and 
suggestions on the measures which appear to be required for the 
further prosecution of the objects for which the observatories were 
recommended. 
The magnetic investigations designed to be carried into execution 
by the Colonial Observatories recommended by the Royal Society 
embraced a much wider scope than had been contemplated by any 
previous institutions, or than had been provided for by the arrange- 
ments or instrumental means of any then existing establishment, 
whether national or private. Not, as previously, limited to obser- 
vations of a single element (the Declination),—or combining at the 
most one only of the components of the magnetic force,—the in- 
structions of the Royal Society, and the instrumental means prepared 
under its direction, provided for the examination, in every branch of 
detail, of each of the three elements which, taken in combination, 
represent, not partially but completely, the whole of the magnetic 
affections experienced at the surface of the globe, classed under the 
several heads of absolute values, secular changes, and variations 
either periodical or occasional,—and proceeding from causes either 
internal or external. To meet the requirements of inductive reason- 
ing, it was needful that the results to be obtained should comprehend 
all particulars under these several heads, attainable by an experi- 
mental inquiry of limited duration. That no uncertainty might 
exist as to the objects to which, in so novel an undertaking, attention 
was to be directed, the Report of the Committee of Physics, ap- 
proved and adopted by the President and Council of the Royal 
Society, stated im a very few sentences, remarkable alike for their 
comprehensiveness and conciseness, the desiderata of magnetical 
science. It may be convenient to reproduce these, when desiring to 
show the degree in which the Observatories have fulfilled their contem- 
plated purposes :—‘‘ The observations will naturally refer themselves 
to two chief branches, into which the science of terrestrial magnetism 
in its present state may be divided. The first comprehends the 
actual distribution of the magnetic influence over the globe, at the 
present epoch, in its mean or average state, when the etfects of tem- 
porary fluctuations are either neglected, or eliminated by extending 
the observations over a sufficient time to neutralise their effects. 
The other comprises the history of all that is not permanent in the 
