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pearance ought to arife from the refradtion of the 
Sun’s rays through Venus’s atmofphere, if fhe had 
one; I carefully looked out for fuch a circumftance, 
but could fee no fuch thing ; neither could I fee any 
ring of light round Venus, a little after hie was got 
wholly within the Sun : but, I confefs, I did not re- 
examine this latter point afterwards, when (he was 
further advanced upon the Sun, at which time other 
perfons at the oblervatory faw fuch an appearance. 
How far the ring of light, which I faw round 
that part of Venus’s circumference which was off the 
Sun, during the immerlion, may deferve to be con- 
fidered as an indication of an atmofphere about Ve- 
nus, I fhall not at prefent inquire ; but I think it very 
probable, that the protuberance, which difturbed Ve- 
nus’s circular figure at the internal contadt, was owing 
to the enlargement of the diameter of the Sun, and 
the contraction of that of Venus, produced by the ir- 
regular refradtion of the rays of light through our at- 
mofphere, and the confequent undulation of the 
limbs of the two planets; the altitude of Venus be- 
ing only 4° 48', though the Sun’s limb was more di- 
ftindt and fteady than ufual at that altitude. This 
conjecture feems corroborated by two circumftances : 
one is, that Venus’s limb, from its firft appearance to 
the total immerfion, as well as afterwards, was very ill 
defined, and undulated very much ; the other is, that 
her horizontal diameter, which I meafured foon after 
the internal contadt with an excellent achromatic ob- 
jedt-glafs micrometer, fitted to the two-feet reflecting 
telefcope, was only 552/h by a mean of eight trials, 
or about 3" lefs than it fhould have been, from the 
obfervations made, with the like inftrument, at the 
tranfit 
