Page:Journal of the Royal Geographical Society of London, Volume 1 (2nd edition).djvu/243

Rh could not be ascertained, Captain Beechey thought it advisable not to introduce the observations into the published tables. The following table will present the result of the observations on dips:—

The observations on the horizontal needle confirm the generally received law, that the intensity of the magnetic force increases as we proceed from the equator to the poles, though the ratio of that increase, as resulting from former experiments, is rather greater than is indicated by the experiments of Captain Beechey. The intensity of the magnetic force, which is in proportion to the square of the number of vibrations made in a given time, is also added to the table of observations, both in its observed and computed ratios.

The observations on the variation of the compass were made with Barlow's plate attached; the local deviation of the needle was ascertained by swinging the ship at Spithead, and the position of the plate determined by the directions which accompanied it. In 1827, it became necessary to alter the position of the plate a little, on account of a different distribution of the iron in the ship. This was done pursuant to experiments made at Petropaulski. These observations, exceedingly minute and numerous, are of the greatest interest to terrestrial magnetism, and, compared with Professor Hansteen's chart of the variations and dip of the needle, furnish additional proof of the accuracy which this branch of science is now attaining. A table is appended, containing the variation of the compass from observations made on shore at different parts of the globe, principally with two of Kater's compasses, the errors of which were 8° 58′ and 2° 18′ respectively.

—Physical Geography, in addition to the history of the mountains, plains, and valleys, or the contrasted configurations of the earth's surface, embraces Geographical Zoology and Geographical Botany; but as the natural history of this voyage is to be published in separate volumes, and as the geographical distribution of the plants or animals can only be connected with an accurate knowledge of the species met with in different places, we must defer any detailed account of these results until the materials furnished by the scientific labours of the