. Appendix to Captain Parry's journal of a second voyage [microform] : for the discovery of a north-west passage from the Atlantic to the Pacific, performed in His Majesty's ships Fury and Hecla in the years 1821-22-23. Science; Botany; Sciences; Botanique. ON THE DIP, Jfrc, AT WINTER ISLAND, lH2lâ2. 265 simple*. If the weight be so adjusted that the needle may be perpendicular, then upon turning the instrument 90 (either way) in azimuth the needle will shew the true dip without any calculation. U the instrument be moved ISO'^ in asiimuth, the needle will shew the magnetic latitude
. Appendix to Captain Parry's journal of a second voyage [microform] : for the discovery of a north-west passage from the Atlantic to the Pacific, performed in His Majesty's ships Fury and Hecla in the years 1821-22-23. Science; Botany; Sciences; Botanique. ON THE DIP, Jfrc, AT WINTER ISLAND, lH2lâ2. 265 simple*. If the weight be so adjusted that the needle may be perpendicular, then upon turning the instrument 90 (either way) in azimuth the needle will shew the true dip without any calculation. U the instrument be moved ISO'^ in asiimuth, the needle will shew the magnetic latitude of the placi> in any part of the world, which is confirmed by experiment. By unscrewing and talcing away this perpendicular stem, and the attached weight, the needle becomes, and may be used as one of the common construction. The needles turned, or vibrated upon horizontal edges of agate, and the instrument was adjusted by means of cross levels for the purpose, in the usual way, by means of foot screws; two distant marks were fixed, one towards the magnetic north, and the other towards the south, to which the instrument was always referred at the time of each observation. The axis of motion of the needle was centrically adjusted by means of a contrivance to elevate or depress it at pleasure, so that it might be placed gently upon the agate edges at each obser- vation, by nu aiis of tinger-screws conveniently placed for the purpose; the ends of the needle mo\ed along a graduated circle in the instrument, divided to S:0 minutes, and the divisions M'cre large enough to be subdi\idcd to 2 or .'{ minutes, by means of two lenses, fixed at the extremities of a moveable arm, concentric with the needle. The fifth eoliunn contains the time taken by the needle, to complete 100 vibrations. The whole arc deseribed in the first vibration was 80, and the last arc not less than o . The number of vibrations between the limits were generally from about ISO to -210, aud the time of completing
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Keywords: ., bookcentury1800, booksubjectbotany, booksubjectscience, bookyear1
