Discussion of the magnetical observations made by Captain Back, R. N., during his late arctic expedition

• Published in: Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1837
• Subjects: Arctic
• Online Access: http://dx.doi.org/10.1098/rspl.1830.0251; https://royalsocietypublishing.org/doi/pdf/10.1098/rspl.1830.0251

The author proceeds, in this paper, which is a sequel to his former communication, to discuss the observations made by Captain Back re­lating to the magnetic intensity, and which were of two kinds; the first, obtained by noting the times of vibration of a needle in the plane of the magnetic meridian; the second, by noting the times of vibra­tion of three needles suspended horizontally according to the method of Hansteen. The results are given in the form of tables. Before deducing results from these observations, the author de­scribes a series of experiments instituted with each needle, for the purpose of determining the corrections necessary to be applied in order to reduce the intensities, which would result from observations made at different temperatures, to intensities at a standard tempera­ture; and he gives formulæ for these corrections. He then determines the relative terrestrial magnetic intensities, at the several stations where observations were made, from the times of vibration of the dip­ping needle in the plane of the meridian, applying the corrections which he had obtained for difference of tem perature; and gives the results in tables. A comparison is instituted between these results and a formula derived from the hypothesis of two magnetic poles not far removed from the centre of the earth. The author considers that this comparison is quite conclusive against the correctness of the for­mulæ, and consequently of the hypothesis itself, if applied to the re­sults deduced from the observations in London, in conjunction with those in America; but that, in the tract of country comprised by Capt. Back’s observations from New York to the Arctic Sea, the phenomena of terrestrial magnetic intensity are very correctly represented by the formula in question.