A. ©. Twining on Occultations by the Moon and Planets. 21 
micrometric measurements are concerned : but ‘the apparent 
motions of certain of the planets—indeed of all the planets in 
certain parts of their revolution—are so sluggish that ;1,” or 
= Tiss Of are would require an ay wrestle time for its 
escription, and consequently for the total obscuration of a star 
of the like diameter. Moreover, suppose that upon rare occa- 
sions in the course of ages certain _— should present themselves 
ely elected to any observer who is able to te Ee deen 
of the hier outline ~qleiing eclipses especially) t 
found in the immediate vicinity of a Be any considerable 
extent of are with an even contour ven a small leng 
from fissures, elevations, or other ere ptible ‘fedpalaritient 
As already proposed I conclud e < some a mse ctal 
sults, obtained in April, 1847, which bear upon the Seapine 
discussion, and which had for ieee ohjedt: a 
* “From the distance of the stars we are naturally led to the consideration of 
their real magnitudes. But here a difficulty arises, which, so far as we can judge of 
4 j ino. must 
; opt ts are capable o P 
—Outlines of Astronomy, Art. 816. 
To ascertain this duration, even approximately, might require the em it 
artificial focal disc both a a and measurable in brightness. Numerous 
arisons with the star occulted having deine, ed, upon the measuring 
of her towely Pog Gan Ice 1 , the auxilia , being 
wi’ Of bewiti w . 
star, one epoch of the observation, of which the other would be, the star’s 
i pin grate 
t tire absence of = seat atmosphere is admitted. But the eclipse 
pt. 18th, 1808—which just missed being <oeec aig at New York—manifested, 
ing to my observat: jin, daring: more than two minutes of time, the distinct 
Phenomenon of of a A agg a aaiek, murky light, completely around the . 
arc of the m 
