/ 



v^ 



44 



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M A T H B: M A T I C A L a^d , 



" In order to difcover the firft external contacS, as near 

 the precife time of its happening as poffible, I kept con- 

 flantly in the field of the telefcope, but a fmall arch of the 

 Sun's limb, and only that part of it, v^here it was expeded 

 the planet would enter; by which means I believe I faw 

 the obfcuration on the limb of the Sun as near the exadl 

 time of Its beginning as the power of the telefcope would 

 admit of. 



" The firft alteration which I perceived in the Sun's difk^ 

 was ci jagged like appearance on a fmall arch of the liml) ; 

 as if a fhaclow had been call on it with an irregular notched 

 edgCy w^hich at every fecond, feemed to increafe with a 

 kind of waving and tremulous motion. I firft perceived 

 this change at 2\ 13^ 47'' apparent time, though I was 

 not then convinced that that appearance was, either the 

 phoenomenon we looked for, or caufed by the planet's 

 near approach to the Sun's limb; but imputed it rather to 

 fome duft that might accidentally have fallen on the large 

 mirror of the telefcope, as I expeded the contafl would 

 have fliewn itfelf by one fmall arched indent on the Sun's 

 limb. And it was not 'till after twelve feconds more had 

 paiTed, that I was certain the contad had happened; for 

 then, vi;2. at 2^I3^59'' apparent time, I could plainly 

 diftingulfh a fmgle imprcffion, or indent, In the Sun's 

 limb; yet it was exceedingly fmall, and without any of 

 the j^ggc^l appearance before mentioned. 



'' I cannot well account for thefe different appearances 

 in fo fmall a fpace of time, but by fuppofmg that the firft 

 was occafioned by an atmofphere around the body of Ve- 

 nus, which might have obfcurcd in a fmall degree, part 

 of the Sun's limb, a few feconds before the conta£l; and 

 that after Venus herfelf had actually entered on the Sun's 

 limb, the brilliancy of the folar rays might have fo far il- 

 luminated the atmofphere of Venus, as to caufe the obfcu- 

 ration at firfl: perceived to difappear, and leave only the 

 well defined form of the planet on the Sun's difk. 



L. 



" On 



