Page:Journal of the Royal Geographical Society of London, Volume 1 (2nd edition).djvu/246

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?14 Captain Bee?hey' s Ymjacje. character, of the discussions which are yet involved iu the results of former experiments, and of the light which they assist in throw- ing on the temperature of the globe and the theory of the earth. The observations made during the expedition of the Blossom were with self-registering thermometers, at various depths, from $0 to more than 700 fathoms; and in all cases it appears that the tem- perature diminishes with the depth to a certain distance, when it begins to increase again, or at least remains stationary; and this depth appears to vary from 300 to 600 fathoms. The experiments at depths beyond this were too few to allow of any satisfactory results; but it appears, as in the experiments of the Russian expedition recorded by Lentz, that below 400 fathoms the tem- peratur? was nearly stationary. The difference of temperature between the surface and a depth of 700 fathoms, as observed by Captain Wauchope, in H.M.S. Euryene, amounted to 31 �There are several experiments made by Captain Beechey, in which the difference amounted to 35 �6 �nd 37 �nd in one case to $9�this was at a depth of 400 fathoms. flit 784 fathoms in the North Pacific, the difference was 36�and in the same place, at 600 fathoms, $7� 760 fathoms, the diffe- rence was $6�and in the same place, at 675 fathoms, 36 �In the South Atlantic, at a depth of $54 fathoms, the difference was only 10� MA G N ?Tl S M.--The observations on terrestrial magnetism were on the dip of the magnetic needle, on the intensity of the magnetic �force, and on the variation of the compass with Barlow's plate attached. The dips were observed with the same instrument which had been used at Melville Island: it had two common needles, and another with a nlOveable weight, fitted up on Pro- fessor Mayer's principle. No. I was used solely for observations on the magnetic intensity, and its poles consequently were never re-. versed; while No. ? and Mayer's were employed for dips, and had their poles changed at each observation. The horizontal needle was suspended in a stirrup by a fine silk, in an octagon wooden box, furnished with a graduated wooden circle on the inside, and covered with a glass top, in which there was. fitted a contrivance for moving the needle out of the magnetic meridian. Until the arrival of the ship at Woahoo, the stay at each place was too short, and Captain 'Beechey's time was too much occupied with astrono- mical observations, and with the business of surveys, for him to give the necessary attention to these delicate observations; but . after that period the observations were regularly m?de. Unfortu- nately for the completion of the series upon the magnetic intensity, the needles used for that purpose became corroded upon the pas- sage ?rom Loo Choo to Petropaulski, by which their magnetic power was much diminished; and as the amount of the change Dig,tiz?d by Google