Mrrson.—On the recent Sun-glows. B67 
been burnt up—unless, indeed, the meteoric dust was in our own orbit and 
moving with our velocity, in which case the phenomena would have been an 
old acquaintance. Other objections to the cosmic dust theory are the 
almost instantaneous appearance and the intermittent character of the 
phenomena. Every re-appearance would imply another cosmic cloud 
moreover; and the amount of meteoric dust requisite to produce the effect, 
would have to be enormous and very exceptional. The number of meteor- 
ites that enter our air daily is computed to be about 10,000,000, weighing 
not less than 100, nor more than 1,000 tons altogether (Langley, ‘‘ Scien- 
tific American"). This amount of matter falling into the air, it is considere4, 
would be far too small to produce the result for which we are seeking the 
cause. A further argument lies in the fact that particles of dust brought 
down by rain and snow-water recently, when subjected to microscopic and 
chemical analysis, are found to resemble voleanie matter rather than mete- 
orie (Professor Rees, New York Academy of Sciences). So that, on the 
whole, it may be concluded that, if it is dust in the upper air that causes 
the sun-glows, that dust is not meteoric but terrestrial. 
IL— Tue Aqueous Vapour Turony. 
The precise cause of the brilliant colouring which so frequently beauti- 
fies the heavens and accompanies the setting and rising of the sun is not 
positively known. It is, however, generally supposed to be owing to an 
extraordinary amount of aqueous vapour (Lockyer, Times, 18th December, 
1883), or dust (Hazen, “ American Journal of Science”) in the higher 
atmosphere absorbing the blue rays which go to the composition of white 
light, and diffusing the red. The connection between red skies and rainy 
weather is recognized in the oldest folk lore. 
Red sky at night is the shepherd’s delight, 
Red sky in morning is the sailor's warning." 
* When it is evening ye say it will be fine weather, for the sky is red. 
And in the morning, it will be foul weather to-day, for the sky is red and 
lowering.” —Matt., xvi., 2, 8. I presume red in the sky in the evening 
does not imply wet weather, but rather the reverse, because it shows us 
that the aqueous vapour in the air is following and passing away with the 
setting sun. Just as the colouring of the deep sea is owing to the refrac- 
tion and decomposition of light passing from one medium into another of 
different density—shallow water appearing, as a rule, colourless—so aqueous 
vapour in the atmosphere causes the absorption of certain component rays 
of white light, and the others being dispersed in the air, impart their 
colour. The ordinary phenomena of twilight and dawn are partly owing to 
the same cause; and it is said that when the sun is seen through the 
funnel of a steam engine it appears green. It was natural, therefore, that 
