One of these modes would be the deposition of dew, which is itself an
illustration of the principle that vapour requires solid or liquid
surfaces to condense upon; dew forms most readily and abundantly on
grass, on account of the numerous centres of condensation this affords.
Dew, however, is now formed only on clear cold nights after warm or
moist days. The air near the surface is warm and contains much vapour,
though below the point of saturation. But the innumerable points and
extensive surfaces of grass radiate heat quickly, and becoming cool,
lower the temperature of the adjacent air, which then reaches
saturation point and condenses the contained atmosphere on the grass.
Hence, if the atmosphere at the earth's surface became super-saturated
with aqueous vapour, dew would be continuously deposited, especially on
every form of vegetation, the result being that everything, including
our clothing, would be constantly dripping wet. If there were absolutely
no particles of solid matter in the upper atmosphere, all the moisture
would be returned to the earth in the form of dense mists, and frequent
and copious dews, which in forests would form torrents of rain by the
rapid condensation on the leaves.
Pages:
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507