VOL. LIX.] PHILOSOPHICAL TRANSACTIONS. 673 



time very nearly, i. e. losing but r in 14 days ; and by transits of the sun, it 

 appeared to be 1'.5 too slow for mean time, on the 3d of June. But by a mean 

 of 8 days' observations of equal altitudes, taken in June and the beginning of 

 July, the clock appeared 5'.2 slower than was found by the transit telescope, 

 which was not perfectly adjusted; though, as its error continued always the same, 

 it was very sufficient for determining the rate of the going of the clock. Hence, 

 on the day of the transit, the clock was &.7 or 7' too slow for mean time; and 

 the observations that follow are corrected accordingly. 



In watching for the first contact of Venus, Mr. W. kept his eye on the sun's 

 edge v/here the contact was expected; keeping that point nearly in the centre of 

 the field ; and the first impression which he saw, witliout any penumbra or at- 

 mosphere that he could perceive, was at 7^ 12"" 32' by his clock, or 7** 12" SQ' 

 mean solar time. The dark part on the sun did not appear with a smooth edge ; 

 and yet he could not discern any undulation in it. Mr. W. tried his strongest 

 magnifying power of ] 10, but to no purpose; for there was an undulation on 

 the sun's edge, by that time, so great, that he thought it best to return to the 

 former power of 55. Before the internal contact, at about 7'' 24"", he lost the 

 sun entirely, and though there were a few breaks in the clouds, he never ap- 

 peared more that evening. 



As to the eclipse the next morning, Mr. W. saw that more perfectly; though 

 at first there were many flying clouds. It began here at IS*" 42"" 17' by the clock, 

 or IS*" 42" 24" mean time (a cloud had just passed; but he can be sure it was not 

 visible 2 or 3' before) ; and it ended at 20'" 28"" 1' by the clock, or 20'" 28"" 8' mean 

 time. The latitude of the place, as well as he could determine by various obser- 

 vations, was 52° 40' 20" north. 



LXIX. Observations of the Transit of Fenus over the Sun, June 3, 17 69; made 

 by Mr. Owen Biddle and Mr. Joel Bayley, at Leivestown, in Pennsylvania. 

 p. 414. 



May 26, 1769, the above observers arrived at Lewestown (on Cape Hinlopen 

 at the mouth of Delaware Bay), being ordered there by the American Philoso- 

 phical Society, held at Philadelphia, for promoting useful knowledge, to take an 

 observation of the ensuing transit of Venus over the sun's disk, and immediately 

 set about fixing their time-piece, telescopes, and equal altitude instrument. The 

 27th, they got some good corresponding altitudes of the sun, by which they set 

 the clock ; and took equal altitudes of some of the fixed stars, to prove the rate 

 of the clock. After this it continued cloudy, with rain at times, and a high wind 

 at north-east, till the 31st, when the clouds broke a little. During this time, 

 they employed themselves in measuring the distance of the place of observation 

 from the stone fixed at the beginning, or east end, of the east and west line, 



VOL. XII. 4 R 



