Contributions to terrestrial magnetism. No. VII

• Published in: Abstracts of the Papers Communicated to the Royal Society of London
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1851
• Subjects: Arctic
• Online Access: http://dx.doi.org/10.1098/rspl.1843.0088; https://royalsocietypublishing.org/doi/pdf/10.1098/rspl.1843.0088

From the discovery which was made of the non-coincidence of the locality of the maximum magnetic intensity, within the Arctic circle, with that in which the magnetic direction is vertical, it followed that the generally prevailing opinions respecting the distribution of magnetic force at the surface of the earth were erroneous, and that even the broad outline of the picture of terrestrial magnetism required to be recast. For the purpose of obtaining sufficiently copious and accurate materials, by means of which so desirable an object could be accomplished, the British Association for the Advancement of Science requested, in the year 1835, a report to be prepared, in which the state of our knowledge, collected from a great variety of sources, with regard to the variations of the magnetic force at different parts of the earth’s surface, should be reviewed, and properly discussed, and suggestions offered as to the best means of extending the inquiry. In the report so obtained, it was recommended that magnetic surveys of that portion of the North American Continent, which is comprised within certain iso-dynamic lines, should be procured. The present paper contains the results of an expedition towards the accomplishment of this object, recommended by the President and Council of the Royal Society to be undertaken under the auspices and with the assistance of the Hudson’s Bay Company. Lieutenant Lefroy, of the Royal Artillery, who had received an appointment to the Toronto Observatory with a special view to this survey, was entrusted with the conduct of an expedition in conformity with that recommendation. The author gives a circumstantial narrative of the expedition, together with minute details of the instruments employed, and the methods of observation adopted; and extensive tables of the observations themselves, both as regards intensity and inclination, at the different stations where they were made, occupying altogether about 120 folio pages of manuscript.