C 68 ] 
the limb of Venus was entering on the fun’s limb 
as in Fig. 20. Tab. III. 
My attention being at this time engaged in examin- 
ing the place around the point of contaft, I endea- 
voured to fee a kind of brown penumbra precede the 
limb of Venus, but fa w none j inftead thereof a 
kind of whitifh light, at firft very faint, and after- 
wards as it advanced on the fun’s difc becoming more 
ftrong, preceded the limb of the planet ; which light 
gradually diminifhed nearer to Venus, and formed a 
narrow margin of lucid matter, whereby the limb 
of the planet became a little ill defined. Almofi the 
fame circum fiances happened in the exterior contadt 
1761, but with this difference, the lucid border then 
following, the limb of Venus was more clear and 
tranfparent. I was the more particular in thefe cir- 
cumftances, to be able to determine what differences 
might arife from obfervations made with telefcopes 
and eyes equally good, and conclude from the phe- 
nomena, that two fuch obfervers, with but little ine- 
equality in their judgments, might differ from each 
other ten feconds of time. Before this contadt and 
a little after it, I endeavoured to find a faint illumi- 
nation on the exterior limb of Venus ; but could find 
none, till the time of internal contadt drew near. 
Another circumftaoce attending the phenomenon was 
this j the limb of Venus which firft entered on the 
fun’s difc appeared to be the arch of a very fmall 
circle j but as the planet advanced onward on the 
folar difc, that fame preceding part of Venus ap- 
peared to enlarge and expand itfelf, and the fubfe- 
quent part of Venus which was on the fun’s limb, 
appeared as though it was the portion of a fmaller 
circle 
