Clouds, in a great measure, prevent radiation, and hence the dew will be most plentiful on a clear and cloudless night. If the radiation continues till the temperature of the ground is very low, the dew freezes as it is deposited and forms hoar-frost.
You may see a smooth road or gravel walk quite dry in the morning, while the grass or box by its side is thickly coated with moisture. Why is this? It is simply because the road or walk is a bad radiator and cools slowly, while the grass and box, being good radiators, become rapidly cold and condense the vapor of the passing air into dew.
Thus by a wise arrangement, the cultivated fields receive an abundance of precious moisture, while not a drop is wasted on the bare rock, or the sterile sands of the desert.
Word Exercise.
- ster´ĭle
- precious (prĕsh´us)
- ĭg´no-rant
- rā-di-ā´tion
- pō´rous
- il-lŭs´trāte
- ăt´mos-phēre (ăt´mos-fēr)
- text´ure (tekst´yure)
- par´ti-cle
- sen-sā´tion
- se-lĕct´ed
- dep-o-sĭ´tion (-zĭsh´un)
- trăns-mis´sion (trăns-mish´un)
- e-cŏn´o-my
- lū´mi-noŭs
- ab-sorb´ing
- in´flu-ence
- cŏn-dŭc´tion
- ar-rānge´ment
Phrase Exercise.
1. Have a tendency to part with their heat.—2. Constant communication.—3. Heat will be propagated.—4. May be handled with impunity.—5. Adapted to impart warmth.—6. Regards it as a protection.—7. Exposed to the influence.—8. Remains unaltered.—9. A simple experiment.—10. Heated intensely.—11. Immediately begin to radiate.—12. Thickly coated with moisture.—13. Wise arrangement.—14. Cultivated fields.—15. Precious moisture.—16. Wasted on the bare rock.