NEW CLOUD CLASSIFICATIONS. 
83 
ways. Its monstrous size indicates a formation out of the 
common. Imagine Mont Blanc (14,134 feet high) lifted into 
the air and set down upon Mount Washington (6,279 feet), 
and you have a fair idea of the dimensions of a medium¬ 
sized cumulo-nimbus cloud. The water in this cloud may 
be cooled below the freezing point and yet not frozen. A 
snowflake or ice crystal falling into it may start sudden con¬ 
gelation, and this, in connection with the electrical condi¬ 
tions, to be alluded to later, may explain the sudden and 
puff-like elongations so characteristic of this cloud. 
In addition to the direction and relative velocity of the 
cloud (the only conditions which have been thus far recog¬ 
nized or utilized in forecasting), it is demanded of the future 
cloud classification that it take into account the level in 
which the cloud is formed and the manner of formation. 
Some such scheme as the following might be profitably used : 
Altitude. 
Formation. 
Cooling by contact. 
Mixture. 
Ascension. 
Electrical 
and 
critical. 
Up to 250 meters..) 
500 .J 
Fogs—haze, dust, 
and ground fogs. 
Nocturnal radia¬ 
tion. 
Nimbus. 
Hail clouds. 
Cumulo-nim¬ 
bus. 
Scud. 
Summer cumuli 
Cumulo-nimbus 
Cumulus. 
750 . 
Stratus. 
1,000 . 
Cu-stratus.... 
Rillows. 
1,500 . 
2,000 . 
3,000 . | 
Ci-cumulus.. 
Cirro-stratus 
Cirrus. 
4,000 . }■ 
5,000 . | 
Alto-cumulus.... 
Above.j 
The altitudes have been kept down purposely, because 
half of the whole amount of vapor in the air is below us at 
a height of 1,800 meters (less than 6,000 feet), and it is but 
fair to assume that the clouds of most importance to us in 
forecasting are those formed below 2,000 meters. Above 
8,000 meters there is practically no water vapor. Most of 
our clouds are formed under the second heading (mixture), 
where condensation results from the mixing of two imper¬ 
fectly saturated currents. Where the mixing is not thorough, 
