defined projections and blending into darker shades caused by the
shadows in the valleys between the mountains of cloud.

The rain cloud is called the nimbus, and may be said to be the extension
of a cumulo-stratus. When it reaches this condition it is condensed to a
point where the vesicular globules collapse and a number of them run
together, forming a solid drop of water, and here it begins to fall. It
may be very small at first, but in its fall other condensed globules
will adhere to it and if the conditions are right, sometimes the rain
drops will have the diameter of a quarter of an inch by the time they
reach the earth.

Under other conditions, such as we have sometimes during dry weather,
the rain drops will start to fall, but instead of growing larger, they
grow smaller by absorption into the thirsty air, and will not be allowed
to reach the earth. Often there are showers of rain in the air that fall
to a certain distance and are taken up, as in the process of
evaporation, to again be formed into cloud, without ever having touched
the earth.

Thus it will be seen that clouds assume various forms under various
conditions of atmosphere, as it is related to moisture, temperature, and
density. Clouds sometimes appear to be stationary when they are only
continually forming on one side and continually being absorbed into
invisible moisture on the other. I remember seeing some wonderfully
beautiful cloud effects in the regions of the Alps. Almost every day in
summer there appears above the peak of Mount Blanc a beautifully formed
cloud cap standing some distance above it and hollowed out underneath
like an inverted cup. Although this cloud appears to be stationary, it
is undergoing a rapid change; the moisture rises from the snow-capped
peak as invisible vapor to a certain distance, where it is condensed
into a cloud of wonderful brilliancy. As the cloud globules float upward
they are absorbed into the atmosphere again, as invisible moisture at
the upper limit of the cloud. If the wind happens to be blowing, another
phenomenon takes place, giving the appearance somewhat of a volcano. It
is blown off from the peak in the direction of the wind, but within a
short distance it strikes a warmer stratum of air, where it is absorbed
and assumes the transparent condition.

If we ascend a high mountain, we get some idea of the altitude of the
various forms of cloud. A thunderstorm may be in progress far below us,
while the