684 PHILOSOPHICAL TRANSACTIONS. [aNNO 1769, 



before the preceding limb of the planet, from which time W. W. took notice 

 that he had told about 24' when the limbs of the sun and Venus were apparently 

 in contact : a circumstance which he did not venture to attend to at the ingress. 

 They saw nothing like the appearance of an atmosphere round Venus (unless the 

 above-mentioned phenomena may be thought to proceed from thence) either at 

 the beginning, end, or during the time of the transit : nor could they see any 

 thing of a satellite; though they looked for it several times. It may not be im- 

 proper to add, that the haziness, complained of at the egress, was not owing to 

 any accidental bad quality of the air at that time; it is continually so here to 10° 

 or 12° above the horizon, and often even to l6° or 18°, in what may be called 

 the clearest state of the heavens. 



Observations for determining the Magnetic Karialions at Prince of Wales s Fort, 

 on the N. fV. Coast of Hudson's Bay, by W. W. 



The variation compass, which Mr. W. received from Mr. Robertson, by order 

 of the Royal Society, was, when he received it, a very good one, as appeared by 

 several trials which he made of it in London, before it was put on board the 

 ship ; but when they arrived in Hudson's Bay, and were ready to make use of 

 it, they had the mortification to find that the needle had, by some cause or 

 other, entirely lost its magnetic virtue. As the cold was, by the time that they 

 made this discovery, much more intense than it probably was at the time that 

 Mr. Ellis complains of a similar circumstance happening to him in those parts, 

 Mr. W. was naturally led to try whether he could not benefit by his experience, 

 and accordingly removed the compass into the room where they lived; which was 

 kept very warm by a large fire, and by the house stove ; and there it remained 

 ever after, but without the least effect. In order to remedy this misfortune as 

 much as lay in his power, he applied to Capt. Richards, as soon as he arrived in 

 the river that year; and desired he would send him his azimuth compass on shore, 

 with which request he very kindly complied the next day; but the cloudy weather 

 prevented him from malting any observations before the 22d of August. The 

 compass was of the common form, and he judged it would be best to make the 

 observations about noon, when the sun's azimuths change the fastest, and to 

 note the times by the clock. By a medium of a great many observations, the 

 variation was ^ A\% west, in the month of August 1769. 



The latitude of Prince of Wales's Fort on the n. w. coast of Hudson's Bay, 

 deduced from a medium of a great multitude of observations of the sun and stars, 

 was 58° 47' 32". 



The instruments used in making the preceding observations were : 1 . A clock, 

 made by Mr.Ellicot, with an apparatus for correcting the effects of heat and cold; 

 the same which Messrs Mason and Dixon had to the Cape of Good Hope in the 

 year 1761 . 2. An astronomical quadrant, made by Mr. Bird, of one foot radius. 



