[ 622 ] 
very laft contadt of Venus with the Sun’s limb, but 
muft have loft fight of it feveral feconds before Ihe 
really had left the Sun’s limb ; and this will the more 
plainly appear, when it is confidered that every fecond 
of the diameter of Venus took up about 19 " of 
time in palling over the Sun’s limb. And to Ihew 
this further, and in a ftronger light, I lhall mention 
the following particulars. Mr. Canton meafured the 
diameter of Venus, and found it — 58'', but by his 
duration of the egrefs, the diameter of Venus is 
— 57 "' ^ : ^ ie f ame diameter was meafured by my 
felf at Savile-houfe, and found — 59", but by the 
duration of the egrefs obferved there, the diameter of 
Venus is = 6. Mr. Mafon alfo at the Cape 
meafured the diameter of Venus, which he found 
— 59", Jj., but by his duration of the egrefs her dia- 
meter is found = 57' , o : and therefore I muft con- 
clude that the diameter of Venus, found by the du- 
ration of the egrefs, muft be always lefs than the 
true diameter for the reafon given above. And, fince I 
am upon this fubjedt, I lhall likewife mention the times 
of duration of the egrefs from feveral diameters of 
Venus. If the diameter of Venus is fuppofed — 57", 
then the duration of the egrefs at London fhould have 
been — 18', 9 " j if the diameter is = 58", then the 
duration at London will be found — 18' 2 S''; and if 
the diameter is = 59", then the duration of the egrefs 
at London will be found — f8' 47 A The diameter 
of Venus being == 5*/', and the diameter of the 
Sun — 31' 31", the duration of the egrefs at Stock- 
olm is — 18' 43", at Paris — 18' 45", at the Cape 
of Good Hope — 18' 8", and at Rome 18' 3 8 A 
The duration of the egrefs at this laft place was ob- 
ferved 
