Frost hollow pockets

1335. It has been remarked, that the hurtful effects of cold occur chiefly in hollow places. If this be restricted to what happens on the serene and calm nights, two reasons, from different sources, are to be assigned for it. The first is, that the air, being stiller in such a situation than in any other, the cold, from radiation in the bodies contained in it, will be less diminished by renewed applications of warmer air; the second, that, from the longer continuance of the same air in contact with the ground, in depressed places than in others, less dew will be deposited, and therefore less heat extricated, during its formation.