Page:Journal of the Royal Geographical Society of London, Volume 1 (2nd edition).djvu/247

From Wikisource
Jump to navigation Jump to search
This page needs to be proofread.

Captain Beechetf s F'otjage. 215 could not be ascertained, Captain Beechey thought it advisable not to introduce the observations into the published tables. The fol- lowing table will present the result of the observations on dips :g /?at. lq'. /?ous. W. Mean dip. bL 1826 N.W. America 70 �? 160 �? 81 � Chamisso Island . 66 12 161 46- 77 39 England. . Egham 69 58 Petropaulskl 58 01 201 15 65 02.8 San Francisco . 87 48 122 2S 62 35.2 Macao 22 12 24? 28 29 57.5 Woahoo 21 18 158 00 40 33 I? Choo 26 12 232 18 35 01.7 Acapulco �. 16 50 99 51 38 58 The observations on the horizontal needle confirm the generally received law, that the intensity of the magnetic force increases as we proceed from the e.quator to the poles, though the ratio of that increase, as resulting ?om 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 com- puted ratios. The observations on the variation of the compass wes'e made with Barlow's plate attached; the local deviation of the needle was ascertained by swinging the ship at Spithead, and the po- sition of the plate determined by the directions which accompanied it. !n 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 Petro- paulski. These observations, exceedingly minute and numerous, are of the greatest interest to terrestrial magnetism, and, compared with Professor Hanstcen'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 dif- ferent parts of the globe, principally with two of Kater's compasaes, the errors of which were $�? and 2 �? respectively. PHYSICAL GEooaAPaY.?Physical Geography, in addition to the history of the mountains, plains, and valleys, or the con- trasted configurations of the earth's surface, embrsces 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 con- nected with an accurate knowledge of the species met with in dif- ferent placest we must defer .any detailed account of these results until the materials furn!.shed by ?h� scientific labours of the Di?,tized by Googlc'