A. 1st—Because valleys contain more moisture than hills: and
2ndly—They are not exposed to so much wind, (which dissipates the vapour).
Q. How does wind dissipate fogs?
A. Either by blowing them away; or else by dissolving them into vapour again.
Q. What is hoar-frost?
A. There are two sorts of hoar-frost: 1.—Frozen dew: and 2.—Frozen fog.
Q. What is the cause of the ground hoar-frost, or frozen dew?
A. Very rapid radiation of heat from the earth; in consequence of which, the surface is so cooled down, that it freezes the dew condensed upon it.
Q. Why is hoar-frost seen only after a very clear night?