6l4 PHILOSOPHICAL TRANSACTIONS. [aNNO 1775. 



of these 4 positions, the dip was taken and noted down 3, 4, or 5 times. And 

 the mediums of all these, for the several places, are as follow. 



J. At Stromness in the isles of Orkney, lat. 58° 59' n., long. 3° 30' w. from 

 London, June 9, 1774. The mean dip was 75" 5l'. 



In these observations the needle was placed horizontal, and the vibration 

 continued between 9 and 10 minutes. The instrument was set in the middle 

 of a room up one pair of stairs ; but being apprehensive that the iron grate, 

 fender, poker, and tongs, might, in some measure, affect the needle, trial was 

 made in the open air, and in a place free from such obstacles. 



2. On the Holms in the entrance of Stromness Harbour, June 23, 1774. 

 Variation per azimuth 24° westerly. Long, from London 3° 30' w. lat. 58° 59' n. 

 Dip. 75° 40'. 



« The needle in all these observations was left to vibrate from an horizontal 

 position. The instrument was set on the top of the case in which it was 

 packed, and stood in the open air, in a fine sunny day, 



3. In Hudson's Straits, July 23, 1774, lat 62" 3' n., long. 69" w. from 

 London, variation 43° westerly. Mean dip, 82° 42'. 



• The needle vibrated from an horizontal situation. These observations were 

 made on a large piece of ice, to which the 3 ships were grappled. 



4. In Hudson's Straits, July 27, 1774, lat 62" 23' n., long. 71° 30' w. from 

 London, variation 42° 50' westerly per azimuth. Dip 83° 1 1'. 



5. In Hudson's Straits, July 28, 1774, lat. 62° 25 n, long. 71° 30' w. 

 from London, variation per azimuth 44° w. Dip 82° 46'. 



6. In Hudson's Bay, August 14, 1774, lat. 5(3° 53' n., long. 85° 22' w. from 

 London, variation per azimuth 24° w. Dip. 82° 41'. 



These experiments were made in the cabin of the Prince Rupert, while she 

 lay among ice. The ship frequently varied the position of her head a point of 

 the compass ; but by replacing the instrument as often as was found necessary, 

 there was the greatest reason to think these observations, which took up above 

 3 hours, are pretty accurate. 



7. At Moose Fort in Hudson's Bay, September 8, 1774, lat. 51° 20' n., 

 long. 82° 30' w. from London, variation 17° w. Dip 80° 13'. 



The observations were made on shore. So remarkable a difference between 

 them, when Mr. H. was expecting quite the reverse, surprized him as much as the 

 increased inclination of the needle from observations made nearly in the same 

 parallel of latitude in London. He endeavoured, by drawing a magnetical 

 meridional line with chalk, and paying the greatest attention to keeping the 

 instrument perfectly steady and horizontal, to render these experiments accurate, 

 and fulfil the intention of the e. s. 



