Q. _Why does the STEAM of a RAILWAY BOILER often pour down, like fine rain, when the steam is "let off?"_ A. The steam from the steam-pipe (when the air is cold) _is condensed by contact with the chill air_, and falls like fine rain. Q. _Why is there LESS DEW when the WIND is EASTERLY, than when the wind is WESTERLY?_ A. _Easterly_ winds cross the _continent of Europe_, and, (as they pass over _land_) are _dry_ and _arid_; but _westerly_ winds cross the _Atlantic Ocean_; and (as they pass over _water_) are _moist_ and _full of vapour_. Q. _How does the DRYNESS of an eastern wind PREVENT DEW-FALLS?_ A. As the easterly winds are _dry_, they _imbibe_ the moisture of the air; and, therefore, there _is very little_ left to be condensed into _dew_. Q. _How does the MOISTNESS of a western wind PROMOTE dew-falls?_ A. As the westerly winds are _saturated with vapour_, they require a _very little reduction of heat_ to cause a _copious deposition of dew_. Q. _When is DEW most COPIOUSLY distilled?_ A. After a hot day in summer or autumn, with the _wind in the west_. Q. _Why is DEW distilled most COPIOUSLY after a HOT day?_ A. Because the surface of the earth _radiates_ heat very freely at sunset; and (becoming thus _much colder than the air_) _chills its vapour_, and condenses it into dew. Q. _Does not AIR radiate heat, as well as the EARTH and its various plants?_ A. No. The air _never radiates heat_, nor is the air itself _made hot_ by the _rays of the sun_. Q. _How is the AIR made HOT or COLD?_ A. By _convection of hot or cold currents_. Q. _What is meant by "CONVECTION of hot and cold currents?"_ A. The air (which is heated by the surface of the earth) _ascends, warming the air_ through which it passes. _Other_ air (being warmed in a similar way) _also ascends, carrying heat_; till _all the air_ is made hot. Q. _Is the AIR made COLD in a similar way?_ A. Yes. The air resting on the earth is _made cold by contact_: this cold air makes the _air above it cold_; and cold currents or winds _shake the whole together_, till all becomes of one temperature. Q. _Why is MEAT very subject to TAINT on a MOON-LIGHT night?_ A. In a bright moon-light night, _meat radiates heat very freely_; and is, therefore, soon _covered with dew_, which produces _rapid decomposition_. Q. _Why do PLANTS GROW RAPIDLY in MOON-LIGHT nights?_ A. In bright moon-light nights _rapid radiation is carried on_, and _dew is plentifully deposited_ on young plants, which conduces much to their growth and vigour. Q. _Why is evening DEW INJURIOUS to HEALTH?_ A. Because the condensed vapours are always laden with _noxious exhalations from the earth_: this is especially the case in _marshy_ countries. Q. _Is HONEY-DEW a similar thing to DEW?_ A. No. Honey-dew is a sweet liquid _shed by a very small insect_ (called the aphis), and deposited in autumn _on the under surface_ of favourite leaves. Q. _Does HONEY-DEW INJURE leaves, or do them good?_