In the East, in the region of Palestine, the dew frequently is so heavy that it closely resembles rain. Upon the great burning deserts alone the dew never falls; for the moment the dew vapours or molecules encounter the scorching breath which arises from the face of these barren seas of sand, they evaporate and are redissolved, dissipated and consumed by the heat. So it will be seen that the fixed molecules which compose vegetation alone have the power to attract and arrest the water molecules of the air with which they come in contact, and thus form, in combination, the dew.
When the temperature is below 32°, the tiny particles which go to form the dew become hoar frost. It is often of great value to the farmer or vegetable grower to be able to know just the temperature of the dew point, because, if he discovers it in time, he is enabled to save his garden from a sudden blighting visitation of the frost.
Another interesting fact, and one which is known to few of us, but which may readily be seen, if we take time to study the dewdrop minutely is; that each tiny drop of dew is in itself a miniature mirror, for upon its clear, crystal-like surface it holds and faithfully portrays upon its rounded form the image of any near-by object. The picture is, of course, naturally inverted. But you will find it; a bit of blue sky holding a scrap of fleecy cloud, or a pigmy forest of trees caught and mirrored in the dewdrop. Often sleeping and dormant insects when caught out in the open during the night, receive a copious deposit of dew. The caterpillar shown in the photograph was a good subject, and quite a collection of dew was deposited upon his furry coat.
[Illustration: 23. A Winter type of hoar frost]
[Illustration: 24. Columnar hoar frost upon a decaying log]
[Illustration: 25. Striking arrangement of hoar-frost crystals upon broken edge of ice, water showing beneath]
Nature in all her moods, and they are many, is always entertaining and instructive, and perhaps one of her greatest marvels is that which takes place in the silence of the brooding night--the falling of the gentle dew.
[Illustration: 26. Showing hoar-frost elaboration about the edge of a leaf]
[Illustration: 27. Hoar-frost deposit upon grass blades]