Observations for determining the dip of the magnetic needle

V. Observations for determining the dip of the magnetic needle. Dip of the magnetic needle observed at Woolwich, and at different stations within the Arctic Circle. In the following Table, is given a general abstract of the dip of the magnetic needle, and of the magnetic intensity, observed at different stations within the Arctic Circle, in the years 1824-25; and of those at Woolwich, both prior, and subsequent to the voyage. The instruments employed in these observations, were those by Jones, and Dollond, already described in the Appendix to the two preceding voyages of discovery; but on this occasion, other needles were added, the whole being numbered as follows: No. 1. A rectangular needle, $7\frac{3}{4}$ inches in length, constructed by Jones on Meyer's principle, having a light cylindrical arm at right angles to its axis, for screwing on a small brass sphere. 2. The same needle, with a sphere somewhat larger. 3. The same needle, with a still larger sphere. 4. A plain rectangular needle of the same length as the above. 5. A needle similar to No. 4, but used only for the intensity. 6. A conical needle, by Dollond, $11\frac{1}{2}$ inches in length, having a moveable axis, for shifting into four different positions; used with the instrument of his construction. 7. A plain rectangular needle, of the same length as No. 6, and used in the same instrument; but employed exclusively for the intensity. It may not be unnecessary to state, that every precaution which suggested itself was taken to insure accuracy, and that the needles were vibrated after each observation, by means of a small piece of magnetised wire, that their axis might not be injured by raising them in the Y's off the agate planes. Each of the registered observations on the dip, were deduced from five readings of the needle, in each of its different positions. The observations for intensity, by means of the time in which the needles performed one hundred vibrations in the meridian, are deduced from the mean of four hundred vibrations, obtained with the face of the instrument on each side of the vertical, and the needles reversed on their axis, in the two positions. | Date | Time of Observation | Latitude North | Longitude West | Observer | Needle | Temperature | Dip of north end of Needle | Mean Dip | Intensity | Remarks, &c. | |------------|---------------------|----------------|----------------|------------------|--------|-------------|----------------------------|----------|-----------|--------------| | 1824 May | | | | WoolwichCommon | | | | | | In Mr. Christie's garden on Woolwich Common. | | 6 | Noon | | | | | | | | | On Boat Island, one of the Whale Fish Islands in Davis' Strait. | | 7 | Noon | | | | | | | | | On the Ice in Davis' Strait. | | June 26 | 5h 37m P.M. | | | | | | | | | At Port Bowen, on the eastern side of Prince Regent's Inlet. | | 26 | 10h A.M. to 4h P.M. | | | | | | | | | The observations in November were partly made by candlelight; those in January wholly by candlelight, and those in April and June by daylight. | | 27 | 8h P.M. to midnight | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 28 | 1h to 4h A.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | July 25 | Noon | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | Nov. 1 | 1h to 3h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 2 | 10h A.M. to 2h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 3 | 10h A.M. to 3h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 5 | 10h A.M. to 2h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 6 | 10h A.M. to 6h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 8 | 10h A.M. to 6h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 9 & 10 | 10h A.M. to 4h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 11 | 9h A.M. to 2h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 12 | 10h A.M. till noon. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 12 | 9h 30m to 2h 30m P.M.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | Jan. 4 | 3h to 4h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 5 | 3h to 4h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 6 | 11h A.M. to 2h 30m P.M.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 7 | 10h A.M. to 2h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 7 | 2h to 6h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 8 | 11h A.M. to 2h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 10 | 11h 45m A.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | April 26 | 11h 30m A.M. to 3h P.M.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 26 | 4h to 7h 30m P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 27 | 6h 15m to 8h 30m A.M.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | June 2 | 9h 20m to 11h 30m A.M.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 2 | 11h 45m A.M. to 1h 30m P.M.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 2 | 1h 50m to 4h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 27 | 9h 30m A.M. to 3h P.M.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 28 | Noon to 2h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 28 | 4h to 6h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 28 | 6h 30m to 9h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 27 | 9h 30m A.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | July 27 | 10h A.M. to 1h 30m P.M.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | Aug. 13 | 8h 45m A.M. to noon.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 13 | 9h 20m to 3h 30m P.M.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 13 | 6h 20m to 7h 35m P.M.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 30 | 8h to 11h A.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | Dec. 3 | 11h 30m A.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 4 | 10h A.M. to 2h P.M. | | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 4 | 2h 50m to 4h 37m P.M.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | | 5 | 1h 30m to 4h 10m P.M.| | | | | | | | | Mean dip of the needle at Port Bowen = 88° 1' 23". | On the eastern coast of North Somerset. Neill's Harbour. In Mr. Christie's garden on Woolwich Common.