It is quite absent in arid regions, in the interior of continents, such as Central Brazil, the Sahara, and Nubia.
360. Why is dew seldom formed at sea?
Because of the defective radiating quality of the surface of water.
361. Why is a heavy dew regarded as the precursor of rain?
Because a heavy formation of dew indicates that the air is saturated with moisture.
Hoar-frost is frozen dew.
363. Why is hoar-frost said to foretell rain?
Because it shows that the air is saturated with moisture, and the temperature of the air being low, the vapours are likely to condense, and produce showers.