METEOROLOGY. (233 
water into a rain cloud, this reflected solar image, for an observer 
sufficiently near the water, may produce the same effect as a sun standing 
below the horizon, and also producing a bow, which then regularly intersects 
the former. The manner in which this intersection is performed depends 
upon the elevation of the sun. Sometimes four rainbows are seen, where 
both the sun and its image produce two bows each. The reason that 
this phenomenon is not visible on the sea is, that the surface is rarely 
smooth enough, and the image of the sun in the waves is generally too 
indefinite. 
A rainbow appearance is sometimes seen in the spray of the sea, or in 
the dew-drops of a meadow, where the curve is generally of an elliptic, 
parabolic, or hyperbolic shape. These bows, as also those seen in the 
mist of waterfalls, &c., are produced by the same causes as actual 
rainbows. 
Lunar rainbows occur but rarely; sometimes they are colored (as at 
Forchheim near Freyberg in Saxony, November 22, 1847), but more 
generally white or yellowish, the feebleness of the moon’s light not 
permitting the colors to be distinguished. 
Of Halos and Parhelia. 
An additional class of very complicated phenomena, likewise dependent 
on atmospheric reflection and refraction, is presented by halos and parhelia. 
We must distinguish two kinds of halo, lesser and greater, which, in 
appearance as well as in constitution, are completely different. The lesser 
halo is a colored ring a few degrees in diameter, seen around the moon. 
more rarely around the sun, when the sky is covered by a pale veil of very 
thin cloud (pl. 25, fig. 9). The red predominates in these rings, and 
sometimes several concentric ones are observed separated by interspaces, 
in which green may be detected. The dazzling action of his rays is the 
principal reason why this form of halo is seldom noticed around the sun. 
They may, however, be very frequently detected by assuming such a position 
as enables us, without looking directly at the sun, to see the contiguous 
portions of the heavens, or by observing the reflection of the sun in still 
water, or in a plate of glass blackened at the back. In June, 1692, Newton 
distinguished three different series of rings at one time: in the first the 
succession of color, commencing nearest the sun, was blue, white, and red; 
in the second purple. blue, green, bright yellow, and red; in the third, 
blue and red. The diameters of the three red circles were five, nine and a 
half, and twelve degrees. The phenomenon is very rare in the perfect 
form; in general, however, it has great similarity to the glory observed on 
looking at the flame of a candle through a glass plate on which lycopodium 
has been strewed. According to Fraunhofer, the phenomenon of these 
halos is produced by the refraction of light, by the vesicles «f vapor in the 
air, as also by the interference of light. 
When the clouds are not so dense as entirely to intercept the passage of 
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