VOL. LrX.] PHILOSOPHICAL TRANSACTIONS. 023 



XXII. Observation of the late Transit of Fenus. By Mr, James Horsfall, 



F.R.S. p. 170. 



These observations were made with a Gregorian telescope, magnifying at least 

 100 times. The time undermentioned is equal time. The rate of going of the 

 two clocks had been correctly ascertained by Dr. Bevis and Mr. H. by observing 

 the sun pass the meridian for several days preceding the day of the transit. 



Mr. H.'s situation was upon a platform laid on the ridges of his own chambers 

 near the Middle Temple Hall: consequently the great volumes of smoke arising 

 from the houses to the north-west were no small impediment to a good obser- 

 vation: this was very remarkable at the time of internal contact. The sun's limb 

 undulated then prodigiously, and there was also a gust of wind which made the 

 telescope vibrate, but not so much as once to lose the planet out of the field. 

 Mr. H. pronounced the moment he saw the internal contact, as soon as he saw 

 a lambent light (not a well-defined light) whirl round the opaque limb of the 

 planet; whence he thinks he pronounced that too early by 2 or 3 seconds. 



The first part of this rare phenomenon, which Mr. H. beheld, was a kind of 

 penumbra, at 7*" 8™ SO*. He then counted 1, 2, 3 to 8*, and plainly discerned 

 the dark limb of Venus make a dent very near the vertex of the sun's limb. At 

 7*' 26"" 34% he perceived the lambent light above mentioned; at which time the 

 sun was not above 4^ of a degree above the top of a chimney. 



XXIII. yin Account of the Observations of the Transit of Fenus and of the 

 Eclipse of the Sun, made at Shirbum Castle and at Oxford. By the Rev. 

 Thomas Ilornsby, M.A., F. R. S. p. 172. 



The weather, on the morning of the 3d of June, was so very unfavourable, 

 both at the observatory of the earl of Macclesfield, and also here at Oxford, that 

 there was very little reason to expect that we should be able to make any obser- 

 vation. But here, a few minutes before noon, the clouds began to break, and 

 Mr. H. was enabled to observe the transit of the sun's consequent limb over the 

 meridian. At one o'clock in the afternoon, the sky was again overcast, and it 

 rained for some time ; but towards 3 o'clock, the clouds were dispersed, the sun 

 shone out clearly, and at 5 o'clock there was hardly a cloud to be seen. The 

 preceding evening was also so very favourable, that the several persons who pro- 

 posed to make observations of the transit, had an opportunity of adjusting their 

 instruments. 



The Earl of Macclesfield made use of an excellent refracting telescope of 3-i^ 

 feet, made by Mr. Dollond, with a treble object glass, magnifying 1 50 times ; 

 and at 7^ 7*" 49' 4 apparent time, was certain that the planet had sensibly ad- 

 vanced on the sun's disk, having seen a small impression on the zenith part of 



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