C. 8. Lyman— Venus as a Luminous Ring. 47 
Art. VII.—On Venus as a Luminous Ring; by Prof. ©. §. 
LYMAN. 
In this Journal,* eight years ago, a brief notice was pub- 
lished of some observations made by the writer on Venus when 
near her inferior conjunction in 1866. The planet was then 
(for the first time, so far as appears) seen as a very delicate 
luminous ring. e cusps of the crescent, as the planet ap- 
proached the sun, had extended gradually beyond a seinicircle, 
until they at length coalesced, and formed a perfect ring of light. 
No opportunity has since occurred of repeating these observa- 
tions until the day of the recent transit. On Tuesday, Dee. 
8th, Venus was again in close proximity to the sun, and the 
writer had the satisfaction of watching the delicate, silvery ring 
enclosing her disc, even when the planet was only the sun’s 
semi-diameter from his limb. This was at 4 P. M., or less than 
These observations were made with a five-foot Clark telescope 
of 42 inches aperture, by so placing the instrument as to have 
could not be used, as there were no means of excluding the 
direct sunlight. 
he morning after the transit the sky was slightly hazy and 
the planet could not be found, though probably it might have 
n if the small telescope had been mounted equatorially. 
On the day following (the 10th), the crescent, extending to 
more than three-fourths of a circle, was seen with beautiful dis- 
tinetness in the equatorial, and on this and two subsequent days, 
measurements were taken with the filar micrometer for the pur- 
pose of determining the extent of the cusps, and consequently 
the horizontal refraction of the atmosphere of the planet, on the 
‘ssumption that the extension of the crescent and formation of 
the ring are due to this refraction. 
The results of these observations are given below, each re- 
sult being the mean of the number o separate measurements 
indicated in the last column. On the 10th, the chord of the 
are between the cusps was measured ; on the other days the 
* Vol. xliii, p. 129. 
