dust blown out by the wind, or possibly by some electrical action between the particles of ice or water-dust.
Pendulous, or Festooned Structure.
In another very marked type of structure the under surface of a cloud is festooned downwards, as in the diagram now before you (Fig. 5), which is from a sketch by Mr. Clouston of Orkney. Up there they call this the "pocky," i.e. the pocket-cloud; while in Lancashire these somewhat globular masses are known as "rain-balls." This is because this cloud is almost the invariable precursor of a heavy shower.
Fig. 5.—The Udders of the Cows of Indra Festooned Clouds.
The poets who wrote the Vedic hymns talk of the udders of the cows of Indra, which drop richness on the earth; and to show how persistently the same idea is suggested by the same formg Mr. C. Ley has proposed the technical name of mammato-cumulus for this shape of cloud.
The modern explanation of festooned clouds assumes that the ascentional column of air which forms flat-based cumulus suddenly fails, and that then the cloud begins to fall downwards.
Flat Lumpy Structure.
Lastly there is a cloud structure, intermediate between flat cloud and rocky cloud, which is known to meteorologists as strato-cumulus.
