METEOROLOGY. 2h7 
In pl. 27, fig. 2 exhibits the appearance presented when the sun stands 
behind a cloud. tg. 3 is an example of the diverging shadow of a layer 
of cumulus combined with cirrus. fig. 6 illustrates the fact that objects 
on the earth, and especially mountains, can cast shadows into space. 
About sunset diverging shadows of great beauty are often seen among 
clouds in the west. If these shadows are long enough to pass the zenith, they 
will converge to a point in the eastern sky opposite to the sun; the opposite 
phenomenon takes place at sunrise. A beautiful illustration of this, repre- 
sented in fig. 5, was observed by Faraday in the Isle of Wight. Ten to 
twelve streaks of light and shadow were visible in the north-east, south-east, 
and south, apparently proceeding in a straight line from a point of the 
horizon between south and east. The atmosphere contained a light fog 
presenting but slight impediment to the sun’s rays. Clouds in the west 
prevented the transmission of light, and immense parallel shadows crossed 
the entire heavens, in an almost horizontal direction. 
We must not omit to make particular mention of the beautiful 
coloring presented by the clouds, especially at time of sunrise and sunset, 
which we shall have further occasion to refer tg in treating of the morning 
dawn. As the clouds principally absorb the blue rays, they generally 
transmit the red, although we may have successive changes to yellow, 
orange, carmine, and purplish red. The situation of the cloud has great 
influence on its colors. In the immediate vicinity of the sun these are 
most brilliant. When directly in front of the sun they appear sometimes 
darker ( pl. 27, fig. 8), and sometimes lighter and colored (fig.9). This 
position of clouds just before the sun, gives rise at times to very interesting 
phenomena. A remarkable case was observed by Howard, where irregular 
streaks existed on a dark cloud, the intervals filled by clouds of a less dense 
but homogeneous texture. When the sun came behind the bright part of 
the cloud, the latter appeared suddenly covered by an irregular and rapidly 
moving network (jig. 10), although the great mass of the cloud exhibited no 
motion. No motion was perceptible when the sun came in contact with 
the dark streaks. Fig. 11 shows the apparent contact of the lower edge of 
the sun’s disk with an upper edge of a layer of cloud. 
Of Rain. 
Rain is produced when, by the continued condensation of watery vapor, 
the separate vesicles unite into drops which are too heavy to float in the 
air, and consequently fall, increasing in size with the descent. To deter- 
mine the amount of rain falling in any one part of the earth, we make use 
of an instrument called a rain gauge, and also ombrometer, udometer, 
hyetometer, pluviometer. &c. One of these is represented in pl. 23, fig. 64. 
It consists of a prismatic or cylindrical tin vessel, B, of five to seven inches 
in diameter, on which rests a second cylinder, open above, and with a funnel- 
shaped bottom perforated in the centre. Rain water falling on A passes 
through the aperture into the vessel B; this, however, is connected by the 
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