'[ i97 ] 
This alone was fufficient to prevent my making any 
obfervations, at that time, which could admit of any 
exa&nefs, if the clouds had not prefently come up, 
and totally deprived me of the fight both of Venus 
and the fun. In this manner the Ikies continued un- 
favourable for about an hour, when they grew again 
extremely clear, and I had the pleafure of feeing Venus 
appear as an intenfely black fpot upon the fun’s body, 
and perfectly well defined. At this time, I mealured 
the diftance of the neareft limbs of Venus and the 
fun from each other, with the curious objedt-glafs 
micrometer adapted to the reflecting telefcope, ac- 
cording to Mr. Dollond’s ingenious invention. This 
diftance was \ f 44*? // > at y h 31™ apparent time, 
©r y h 2 9 m I5 f mean time. I think it proper to take 
notice, that though Venus’s limb and the fun’s ap- 
peared as well defined, as could be defired ; yet, when 
the artificial internal contact of Venus’s limb with 
the fun’s was made, in order to meafure their di- 
Itance, Venus’s limb alternately dilated itfelf over,, 
and contracted itfelf within the fun’s limb, by a fmall 
fpace. I endeavoured to take it in the middle of this 
vibration ; but I beg leave to refer it to your Lord- 
Ihip’s opinion, whether, if the real internal contaCt 
had happened at this time, it could have been ob- 
ferved, in fuch circumftanees, to that degree of exaCt- 
nefs, which the great Dr. Halley hoped for; and 
whether, on occafion of the next tranfit, which is 
to happen eight years hence, it might not be conve- 
nient, that, the obfervers Ihould endeavour to place 
themfelves on fuch parts of the globe, as that they 
may not fee Venus on the fun’s body, very near 
the horizon, but rather when they are both elevated 
