Year: 1865

What, then, is the cause of the wind
The simple answer is--the sun. II you
light fe in the room, and afterwards !
stop up every clink by which air can gain
access to the fire, except the chimney, the
fire will 20 out in a short time, Again, il ,
lamp is burning Gu the table aud .you
stop up the chimney at the top, the fame
will 90 out at once, The reason of this is,
that The flames, ia each case, attracts the
air. and if either the supply OF air be cut
of below or its escape above is checked,
:ho hame cannot continue to burn.--
This explanation, however, does not bear
to be pushed too far. The reason that
the fire goes out if the supply Of air is cut
of, is, that the flame is not fed; while the
sun cannot be said, in any scuse, so be
dependent on the earth atmosphere for
the fuel for its llrc We have chosen the
illustration Of The flame because the facts
are so we'll known. If, instead Of flame
in the middle OF the room, we were to
hang up a large mass nj heated iron, we
should find currents Of air set in from all


sides, rise up above il, aud spread out
! when they reached TIE ceiling, descending
again along the walls, The existence OF
these currents may be easily proved by
sprinkiiDg handful OF Gne chat about IN
the room. What is the reason of the cir.
cuation thus produced : The iron, un-
less it be extremely hot, as it is when
melted by Mr.. Bessemers process, does
not require the air to keep up its beat !;


and in fact, the constant supply Of fresh
air cools it, as the metal gives away its
OWL heat to the air as fast as the parti


cles Of the latter como in contact with it.


Why, then, do the currents rise Be-
cause the air, when heated, expands or
gets lighter, and rises, leaving an empty
space or vacuum where it was before
Then the surrounding cold air being clas-
tic, forces itself into the open space and
gets heatc in its turn. From this we
can see that there will be a constant ten.
dency in the air TO flow towards that
point on the earlh's surface where the
temperature is highest-or, other things


being equal, TO that point where the sun


may be at that moment in the zenith
Accordingly if the earth's surface were
either entirely dry land or entirely water,


and the sun were continually in the plane


OF the equator, we should expect to fud
the direction of the great wind currents


permanent and unchanged throughout the


year. The true state oil the case is, how


over, that these conditions are very iaI


from being fulfilled. Every one knows


that the sun is not always Immediately


over the equator, but that he is at the


tropic oil Cancer in June and a: tho tropiC
Of Capricorn in December, passing The
equator twice year at tho equinoxes.-
Here, then, we have one cause which dis


turbs the regular flow OF the wind current
The effect of this is materially increased
by the extremely arbitrary way in which
the dry land has been distributed owe
the globe, The northern hmisphere con
3 taius the whole of Europe, Ashland Norll
Q America, The greater part OF Africa, an'
o portion Of South America while in tn
r., Southern Hemisphere we ouly find tn
+, remaining portions of the two last name'
Q continents, with Australia and some of th
d large islands in the vicinity. According


ly, during our summer there is a much
r greater area OF dry land exposed to tn


nearly vertical rays Of the sun than is tn
n case during our wiOter,