VOL. LX.] PHILOSOPHICAL TRANSACTIONS. &g 



But what principally engaged his attention this evening, was a luminous arch, 

 or zone, of a very beautiful purple colour, such as he had never seen before ; 

 which presented itself to view about 8*' 40". P. M. and extended from E. to w. 

 nearly bisecting the hemisphere. This became fainter a little before Q o'clock ; 

 and in less than 10 minutes* time totally disappeared. 



The light cast by the aurorae boreales above-mentioned was greater than any 

 he had ever observed to attend such phenomena before. Nor did he ever meet 

 with a description of any meteors resembling that mentioned here in every 

 particular. The conversion of the flame-colour, in the first stage of the 

 meteor, into a deep blood-red, with its wonderful expansion, and the beautiful 

 purjjle zone, or coloured arch, which closed the whole, are singularities that 

 probably never occurred before ; or at least, such as have never hitherto met 

 with a proper and adequate description. Some of these phenomena seem, from 

 the public papers, to have been seen at London, Windsor, and other places at a 

 considerable distance from Oxford, about the same time that they appeared there; 

 which remarkable circumstance, on several accounts, merits a place in this letter. 

 The whole city, for a short time, seemed to be perfectly illuminated ; the light 

 cast by the aurorae succeeding the luminous apjiearance of a deep blood-red 

 colour, being much superior to that of the full moon. In fine, the whole phe- 

 nomenon (or rather all the phenomena) was so very striking and remarkable, 

 that it was one of the most common topics of conversation, among all orders 

 and degrees of people here, for above a month after it appeared. 



XLVII. On the Effect of the Aberration of Light on the Time of a Transit 

 of Venus over the Sun, By Rd. Price, D.D., F.R.S. p. 336. 



Dr. P. does not doubt but that the observation made by M. Winthrop, in 

 a former paper, is right. The aberration of Venus must, he thinks, affect the 

 phases of a transit, by retarding them, and not by accelerating them. This 

 retardation is 55^; for that is the time nearly which Venus, during a transit, 

 takes to mo":. aver 3".7. This, however, is by no means the whole retardation 

 of a transit occasioned by aberration. There is a retardation arising from the 

 aberration of the sun, as well as from that of Venus, The aberration of the 

 sun, it is well known, lessens its longitude about 20" ; and the aberration of 

 Venus, agreeably to Mr. W.'s demonstration, increases its longitude at the time 

 of a transit 3".7. Therefore Venus and the sun, at the instant of the true 

 beginning of a transit, must be separated from one another by aberration 23".7 ; 

 and since Venus then moves nearly at the rate of 4' in an hour, it will move 

 over 23". 7 in 5™ 5.5'. And consequently from the instant of the real beginning 

 of a transit, 5™ 55' must elapse before it can begin apparently. 



It may be objected, that the aberration of the sun ought not to be taken into 



VOL. xiir. N 



