VOL. LII.3 PHILOSOPHICAL TEANSACTIONS. 555 



June to Monday evening the 8th June; so that he was as sure of the time at 

 Savile-house, as if the obwservation had been made at his own house in Surry- 

 street. 



XXX IF. On the Transit of Fenm^ June 6, 1761, made in Spital-Square; the 

 Longitude of which is A' \\" West of the Royal Observatory at Greenwich 

 and the Latitude 5 1"" 31' 15'^ North. By John Canton, M.A., F. R. S. p. 182. 

 Having measured the diameter of Venus on the sun 3 times, with the object- 

 glass micrometer, the mean was found to be 58 seconds; and but -j^ of a second 

 the difference of the extremes.* 



The diameter of the sun, from 4 observations very nearly agreeing with each 

 other, was 3l' 33' 24"'. 



The time, by the clock, of the internal contact, was 8^ 17"" 4' 



Of the external contact 8 35 27 



Of noon 11 58 24-1. 



Therefore the apparent time of the first contact was 8 18 41 



Of the last contact 8 37 4 



These observations were all made with a reflecting telescope of 1 8 inches focal 

 length, which magnified about 55 times. 



XXX F. Observations of the Planet Fenus, on the Sun^s Disk, June 6, 176I; 

 and Certain Reasons for an Atmosphere about Fenus. By Samuel Dunn. 

 p. 184. 



The latitude of his place was 51° 29' 5" n. and 41* of time west of the ob- 

 servatory at Greenwich, between the physic-garden and Chelsea hospital. 



With the 6-feet Newtonian reflector, and its magnifying power of 110, and 

 also of 220 times, he carefully examined the sun's disk, to discover a satellite of 

 Venus, but saw none ; for he had a very clear dark glass next his eye, and the sun's 

 limb appeared most perfectly defined; but a very narrow waterish penumbra ap- 

 peared round Venus, by which its limb was not perfectly defined, and at the 

 distance of about a 6th part of Venus's diameter from its edge, was the darkest 

 part of Venus's phasis, from which to the centre an imperfect light increased, 

 and illuminated about the centre. 



At 8^ 16*" by the clock, he was prepared to observe the internal contact ; and 

 as Venus drew nearer to the sun's limb, the penumbra near the limb of Venus 

 became darker, and threatened to obscure the point of contact at the instant it 

 would happen. 



•With the same micrometer, the diameter of Venus was measured, off the sun, 12 times, 

 March 29th, 1758, about noon ; and the mean was 1' 1" 42'"; whence the diameter, at the time of 

 the transit, ought by computation to have been V 0" 19'". — Orig. 



4 B 2 



