Part 48 (1/2)
Q. _How does RETAINING their COLD account for their being so WET?_
A. As the vapour of the warm air _touches the cold wall_, it is _chilled_ and _condensed into water_, which _sticks to the wall_, and sometimes trickles down in little streams.
Q. _Why does a thick WELL-BUILT HOUSE contract more DAMP of this kind, than an ORDINARY one?_
A. Because the walls are much _thicker_; and (if the frost has penetrated _far into the bricks_) it takes a long time to reduce them to the _same temperature as the air_.
Q. _Why are BANISTERS, &c. DAMP after a THAW?_
A. The wooden banister (being made of some very close-grained, varnished wood) cannot _change its temperature so fast_ as the air; and, therefore, _remains cold_ some time after the thaw has set in.
Q. _How does THIS account for the BANISTERS being DAMP?_
A. The vapour of the warm air (_coming in contact with the cold banister_) is _chilled_, and condensed into _water upon it_.
Q. _Why is our BREATH VISIBLE in WINTER and NOT in SUMMER?_
A. In _winter_ the coldness of the air condenses our breath into _visible vapour_; but in _summer_ the air is _not cold enough_ to condense it into visible vapour.
Q. _Why are our HAIR and the BRIM of our HAT often covered with little drops of pearly DEW in winter-time?_
A. The breath (issuing from our mouth and nose) _is condensed into drops_, as it comes in contact with our cold hair or hat; and (being condensed) hangs there in little dew-drops.
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 pa.s.s over _land_) are _dry_ and _arid_; but _westerly_ winds cross the _Atlantic Ocean_; and (as they pa.s.s 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?_