A. If we suppose the brass meridian to be the vertical sun, the whole column of air _beneath_ will be heated by the _noon-day rays_; that part which the sun has _left_, will become gradually _colder and colder_; and that part to which the sun is _approaching_, will grow constantly _warmer and warmer_. Q. _Then there are THREE qualities of air about this spot?_ A. Yes; the air over the place which _has passed the meridian_ is _cooling_: the air under _the vertical sun_ is the _hottest_; and the air which is over the place _about to pass under the meridian_, is _increasing in heat_. Q. _How does this VARIETY in the HEAT of AIR produce WIND?_ A. The air always seeks to _preserve an equilibrium_; so the _cold air_ rushes to the _void_, made by the _upward current of the warmer air_. Q. _Why does not the wind ALWAYS BLOW ONE way, following the direction of the SUN?_ A. Because the direction of the wind is subject to perpetual interruptions from _hills and valleys_, _deserts and seas_. Q. _How can HILLS and MOUNTAINS ALTER the course of the WIND?_ A. Suppose a wind, blowing from the north, comes to a mountain, as it cannot pass _through it_, it must either rush _back again_, or _fly off at one side_ (as a _marble_ when it strikes against a _wall_). Q. _Do MOUNTAINS affect the wind in any OTHER way?_ A. Yes; many mountains are _capped with snow_, and the _warm air_ is _condensed_ as it comes in contact with them; but as soon as the _temperature of the wind_ is changed, its _direction_ may be changed also. Suppose A B C to be _three columns of air_. A, the column of air which is _cooling down_; B, the column to which the _sun is vertical_; and C, the column which _is to be heated next_. In this case the _cold_ air of A will rush towards B C, because the air of B and C is _hotter_ than A. But suppose now C to be a _snow-capped mountain_. As the hot air of B reaches C, it is _chilled_; and (being now _colder_ than the air _behind_) it rushes _back again_ towards A, instead of following the sun. Q. _How can the OCEAN affect the direction of the WIND?_ A. When the ocean rolls beneath the _vertical sun_, the water is _not made so hot_ as the _land_; and (as another _change of temperature_ is produced) another obstacle is offered to the _uniform direction of the wind_. Q. _Why is not the WATER of the sea made so HOT by the vertical sun, as the surface of the LAND?_ A. 1st--Because the _evaporation_ of the sea is greater than that of the land: 2ndly--The waters are _never still_: and 3rdly--The rays of the sun strike _into_ the water, and are _not reflected from its surface_, as they are by _land_. Q. _Why does the EVAPORATION of the sea prevent its surface from being HEATED by the vertical sun?_ A. As water _absorbs_ heat by being _converted into vapour_; the surface of the sea is continually _losing heat by evaporation_. Q. _How does the MOTION of the sea prevent its surface from being HEATED by the vertical sun?_