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ASTRONOMICAL PAPERS. 



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The parallax of the Sun bciiig fiKcd by the meaa o 

 fuch coiBparifons as tliefe, it is an eafy matter to afcertaia 

 not only the diftances of the bodies, which conipofc the 

 folar lyftem, but alio their real diameters; that of tlxe 

 earth being previoufly known from the a£tual menfuration 

 of fome degrees on it's furface. For 



As the rectangle of the parallax of the Sun, and his 

 diftance from the earth, is to the real diameter of the earth j 

 fo is the reftangle of the parallax and diftance of any other 

 planet from the Sun, to its real diameter. 



delineation of the tranfit^ T hav 

 ■)f the projeB'ion from our oivn ohj. 



of J' 



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HE nearcft approach of the centers having been de- 

 termined, from the mean of a great number of com- 

 putations, and found to agree very nearly with the mea- 

 furcs that were adually made at the middle of the tranfit, 

 it vi^as accordingly fet off on the diameter of the Sun, and 

 through this point a cliord was drawn at right angles to 



the faid diameter for the central tranfit line. This was 



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then divided carefully into hours and minutes^ according 

 to the horary motion of Venus, determined by tlie pre- 

 ceding: calculation, in fuch a manner, as that the exa£t mo 



ment of the middle of the tranfit, at the earth's center, 

 fhould fall on the point of interfedion between tlic faid 

 diameter of the Sua and tranfit line; this moment of time 

 having been previoufly determined, by the mean of a fuf- 

 ficient number of computations. 



The parallaxes of Venus, in longitude and latitude, as 

 ktw from Philadelphia, having been alfo adapted to the 

 apparent times of the micrometer meaiurcs, on the fuppo- 

 fition of the Sun's horizontal parallax being 8^^,5204 on the 

 day of the tranfit, they were accordingly applied to the pro- 

 jcdion, by which the places of her center were determined 

 for the f^iid times. Round thefe, fmall circles w^ere drawn, 



with the radius of 29 feconds, to rcprefent the diflc of 



Venus 



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