VOL. LX.] PHILOSOPHICAL TRANSACTIONS. Ql 



sun's centre at the calculated moment of a conjunction, will be 75''.Q, over 

 which it will move in 19 minutes of time. And this, consequently, will be the 

 retardation of the phases of a transit of Venus occasioned by aberration, on 

 the supposition, that in calculating, the sun's apparent, and not his true place 

 is taken. 



In a postscript to this letter Dr. P. says : in a former letter, I gave, by 

 mistake, the error occasioned by aberration, less than I have now given it. The 

 discovery of this mistake I owe to the kind assistance and correction with which 

 Mr. Maskelyne, the astronomer royal, has been pleased to favour me. I have 

 for the sake of more distinctness and clearness, supposed Venus to move in the 

 plane of the ecliptic. Some differences will arise from the inclination of the 

 path of Venus to the ecliptic, and also from taking the aberration of the sun, 

 and the proportion of Venus's distance from the earth to her distance from the 

 sun, exactly as they really are at the time of a transit. Thus, at the time of the 

 last transit of Venus, supposing light to come from the sun to the earth in 8™.2, 

 the aberration of the sun was IQ^.S. The distance of Venus from the earth was 

 to its distance from the sun as 29O to 726, and therefore the retardation 

 18"" 16'. Mr. Canton has observed, that in the Con. des Temp, Mr. De la 

 Liande makes the effect of aberration, at the inferior conjunction of Venus and 

 Mercury, to be an augmentation of their longitudes. Indeed, Mr. Bliss himself 

 observes this ; and yet through an ovesight, makes the effect as to time to be an 

 acceleration. Vid. Phil. Trans,, vol. 52, p. 249. 



XLVIII. A Catalogue of the Fifty Plants from Chelsea Garden, presented to 

 the Royal Society by the Co. of Apothecaries, for the Year 1 769, pursuant to 

 the Direction of Sir Hans Sloane, Bart. By JVm. Hudson, F. R. S. p. 54i . 

 This is the 48th presentation of this kind, completing to the number of 2400 



different plants. 



XLIX. A Short Account of the Observations of the late Transit of Venus, 



made in California, by Order of his Catholic Majesty, by Don Vincent Doz. 



Communicated by his Excellency Prince Masserano, Ambassador from the 



Spanish Court, atid F. R. S. p. 649. 



Don Vincent Doz, commander of a Spanish frigate, is just arrived at Madrid. 

 He brought with him, and presented to the king, an account of his observation 

 of the last transit of Venus at California, whither he was sent last year for that 

 purpose, being in substance as follows ; 



The latitude of the village of St Joseph, 8 leagues distant from Cape St. 

 Lucar 23° 5' 15'; the longitude from the meridian of Paris 7'' 28'" 17V; the 

 two internal contacts of the planets were at ] 7"" 23", and at 5" 54" 44^^'. Hence 



N 2 



