LUMINOUS PHENOMENA. 
69 
the boonJary of a large corona : it is generally of less diameter 
than usual, and often c iloured with the tints of the Iris. A 
beautiful one appeared on the 22d of December, I 8 O 9 , about 
midnight, during the passage of a cirrostratus before the moon. 
CoKONA. Discus lucid'ts, vel pnrlio circularis nulls reliqvd Corona. 
lucidior, in c ijus centra Sol aut Luna videlur. 
Ohser. When the sun or moon is seen through a thin cloud, 
a portion of the cloud, ntore immediately round the sun or 
moon, appears much lighter than the rest of it: this luminous 
disk, if I may be allowed the expression, I call a corona. 
Coronae are of various sizes, according to the peculiarities of 
the intervening vapour : but they seldom exceed 10 in diame- 
ter : they are generally faintly coloured at their edges. 
Frequently, when there is a halo encir..hng the moon, there 
is a stnall corona ntore imn.edialely round it. Coronae, as 
well as halones, have been alw.iys observed to prognosticate 
rain, hail, or snow. As far as I can observe, they are generally 
seen in the cirrostratus cloud. 
Corona duplex. Discus lucidus, aliiim discum paulo luci- Double 
diocem ac minorem includens, in quorum centra communi Sol 
vel Luna videla. 
Olser. A double corona is very Common : so.nietimes they 
are triple or quadruple. 
Parhelion. Def. Imago Solis falsa, vel plures imagines Parhelion, 
eiusdem generis circa Solrm circulalim dispositce, et magis 
minusve ha/onilus aliisque lucidis vitlis comitatte. 
Ol'ser. Parhelia vary considerably in general appearance : 
sometimes the sun is encircled by a large halo, in the circun’fe- 
rence of which the mock suns usually appear : these have often 
small halones round them : they have usually a horizontal band 
ot white light, of a pyramidal figure, extending from them : 
sometimes a large semicircular band of light, like an inverted 
arch^ seems to rest upon the halo which encircles the sun : but 
these 
