216 
THE OPTICAL PHENOMENA OF THE 
ATMOSPHERE. 
HOSE appearances in tlie heavens, such as the Rainbow, the 
Aurora, &c., which frequently present themselves to the 
gaze of man, although perhaps only for a brief space of time ; 
and which, during that time surprise him by their brilliancy and 
beauty, were amongst the first external phenomena in nature 
that impressed themselves upon his dawning intelligence. 
And yet, as we often find to be the case, those very common- 
place phenomena, which have been witnessed from time 
immemorial, are less understood than are the less striking ones, 
which, from the rarity of their occurrence, rivet the attention 
and lead to various speculations as to their nature. 
It is our intention in the present paper to say a few words 
concerning these ordinary optical phenomena. 
The Rainbow is one of the prettiest, as it is also one of 
the commonest atmospheric appearances with which we are 
acquainted : it is never seen but in showery weather, when the 
Sun illuminates the falling’ rain, and the spectator turns his 
back to the Sun, whose elevation above the horizon must not 
exceed 42°. 
The earliest historic mention of the Rainbow is in Genesis 
ix. 18, where it is mentioned in connection with a pledge from 
the Great Ruler of the Universe that this Earth should never aomin 
O 
be overwhelmed with another general deluge. 
Homer says — 
“ Like unto rainbows, which the son of Saturn 
Hath fixed in a cloud, a sign to articulate speaking men,”* 
Virgil speaks of Venus as — 
“ The Virgin goddess, seen by none, hastening her journey through 
A how of a thousand colours, glides down with a nimble tread.”f 
Various speculations are to be found in the works of old 
BY G. F. CHAMBEFS 
* Iliad , lib. xi, line 28. 
f 2Eneid, lib, v. line 609. 
