34 



M 



AND 



/ 



apparent time. This line was then divided caretully 

 into hours and minutes, fuppoiing Venus to move 240, 36 

 over the Sun's Diflc in an hour, accordmg to a calculation 

 1 had formerly made from Halley's tables. Ihe p ace of 

 Venus's center in the tranfit line, was then marked to the 

 times of each of the obfervations ; ar^d from Aence the ap- 

 parent place of her center found, by fettingofF the quantity 

 of her parallax from theSun in its proper diredion. About 

 each of the centers fo found, a circle is defcribed with the 

 radius 28' ,?6. the obfcrved femidiameter of Venus. Blank • 

 iTnes were next drawn through the Sun's center and the 

 nnnarent place of the center of Venus; and on theie the 

 S line? were drawn from the Sun's limb precifely of 

 fach length as we found they ought to be by the micro- 

 meter • fo that it may be feen at once how far they corre- 

 lV)ond with each other, by obferving how much they exceed 

 or fall il^ort of reaching the limb of Venus. 



Out of the 1 8 micrometer obfervations, there is fo exad 

 a correfpondence among 14 of them, that lam well con- 

 vinced they may be depended upon. Two of the others, 

 as will appear by the figure, reach about ^ J ccond ov^rihc 

 limb of Venus ; and the other two are fcarce ^Jecond fhor 

 of it Such fmall differences might eafily have happened 

 for the leaft inaccuracy in reading off the time, or the divi- 

 fions of the vernier, or from their not being exadlly taken 

 in the diredion of the ncareft diftance of the limbs; that is 

 in a line joining the center of the Sun and Venus ■ 



The meafures intended to be taken in chords parallel , 

 to the equator, are likewife exceeding near the truth if it 

 be confidered in fctting the micrometer to that direction, 

 we had only the truth of the polar axis to depend on, which 

 was conUraQcd haillly to anfwer the purpofe, of the day. 

 Three of thefe meafures agree well with each other, and with 

 all the other micrometer obfervations, on fuppofing the 

 chord in which they were taken inclined half a degree to 

 the plane of the equator. The 4t]i is ftUl more nearly pa- 

 ralld, but diverging fomcthing the other way. Thee 



1 







