6
ON
SOME OE THE RESULTS
OBTAINED AT THE
BRITISH COLONIAL
MAGNETIC OBSERVATORIES.
At the meeting which took place at Newcastle in 1838, the British Asso-ciation, in fulfilment of the first amongst the objects for which it was originallyinstituted,—that of giving a stronger impulse and a more systematic directionto scientific inquiry,—recommended to Her Majesty’s Government the pro-secution at the public expense of researches which were required for the ad-vancement of the science of terrestrial magnetism, but were beyond the meansof individuals to carry out. These researches were of two kinds, having differ-ent, but in many respects connected objects. By one class of observations,for which the aid of naval expeditions to unfrequented parts of the oceanwas required, it was desired to determine the distribution in different partsof the globe of the magnetic force of the earth in its two manifestations ofdirection and intensity of action. By the other class of observations, to bemade at stationary observatories placed at points of the earth’s surface verydistant from each other and judiciously selected, it was proposed to ascertainthe particularities of the change w'hich is found to take place from year toyear in all parts of the globe in the direction and intensity of the magneticforce, by which change the magnetic state of the earth corresponding toany one epoch passes, as it were, insensibly, but with a regularity and sy-stematic order which manifest the existence of natural causes as yet unknownto us, into successive forms of distribution, which, after the lapse of con-siderable intervals of time, are found to differ very widely from each other.This change has received the name of secular change. By this second classof observations it was also proposed to trace the laws, and, if possible, thecauses, of certain small periodical and other variations, superimposed uponthe mean magnetic state of the globe, which, at the time when the observa-tories were undertaken, were generally believed to be in some way or otherconnected with the variations in the temperature of the earth or of the air.
For such observatories, our colonial possessions, dispersed as they are inalmost all parts of the globe, and presenting almost every variety of climatesuitable for a thorough examination of the supposed connexion between theniagnetical and meteorological elements, afforded excellent positions; and it"as believed that amongst our naval and military officers employed for the