The Pacific commercial advertiser. [volume] (Honolulu, Hawaiian Islands) 1856-1888, 1878-07-27
WATER N VAPOR.
An Essay Read Before the Hawaiian Mission
Children's Society.

Every one appreciates the value of water; and the
part IL plays ia the economy of nature, whether as a
solid, liquid or vapor, cannot fail of being "a matter
OF Interest to every inquirIng mind. Ii Is our par
pose, IN the following article, to call attention TO
some of its more striking characteristics as a vapor,
and the important relations which they bear to the
welfare OF our giohe.
All energy at work on the surface of this planet
comes from the sun. Silently but surely it raises
FROM the ocean the vapOr which returns AS rain aud
dew to clothe with beauty aud verduIe the waiting
earth. lis genial rays quicken and sustain all ami
nal and vegetable life. Oar everyday eXpe-
rience associates these rays OF light and heat 50 iu-
tImately, that 1t 10 natural for US TO suppose that any
cause which affects the one will cOTrespundingly
affect the other, and that any screen which cuts of
one class OF rays must necessarily cut oil the other
class as we'll. y careful Investigation of this sub
ject by Tyudall and others has proved, however, that
this Is not the Case, and that transparency to light
does not necessarily imply transparency TO radiant
heat. Ice, for example, though IL allows the rays OF
light to pass freely through II, Is almost Opaque to
heat rays. Tie same is true of water. Gu the
other hand, If the suns rays are caused to pass
through bisulphiIe OF carbon in which iodine is dis
solved, this OPAQUE liquid quite shuts of the rays of
light, while it permits the rays of heat to pass with
scarcely any dimiuutOn ia their intensity. Again,
"a plate of rock-salt allows both classes of rays to pass
through It simultaneously. We thus see that diff
ferent bodies tehave very differently with respect to
their transmission of light aud heat rays. Pure dry
air is a mixture Of Two simple gases, oxygen and
nitrogen.
Either Of these gases alone, or the two mixed
together as air, are TO be Clas>Cd, with rock-saii,
among those bodies which are equally transparent to
light and heat. But unlike the latter, they seem to
offer no appreciate resistance to the passage Of
either class of rays, anu for all practical purposes
may be considered as perfectly transparent to 10th.
The ordinary air OF the atmosphere is, however,
never completely dry. ere Is always ditiused
through it a certain amount of aqueous vapOr.
by the term vaPor We do not mean a cloud, or q
fog, or II mist, or anything visiple. II is AS clear rs
the air itself, and when condensed TO cloud or mist
is 10 longer vapOr, but minute PARTICLES of water
suspended in the mir. How often. as We gaze at a
distant mountain, We are charmed with a rich tint
of blue which grows less and less aud finally van
ishes as we approach.
This rich - atmospheric effect" ms the artist is
wont to call it, is due to the aqueous vapor, the blue
deepening with the amount of it in the air That
which is to be most noticed in regard to this vapor
is the fact that, like ice and water, while go trans
parent to light, it is quite Opaque to rays of heat.
Though its relative quantity Is small, less than one
two-hundredIh part Of our atmCsFh' re, yet this COM
narativsly insignificant amount acts powerfully rs a
screen TO protect Us from the Oihe' wise uueHdurttie
heat of the suns rays, ard OF only hat; NJ night il
serves ns "A blanket to retain the heat of the earth
accumulated during the day, which would, hu' for
this invisible covering, expand itself by radiation
into empty space. leaving the surface of the earth
ii night cold and ljfeiess, 10 be again parched by the
burning rvs of the returning sun. On the tops of
lofty mountains there is an enormous difference in
the warmth of objects protected By Il shade, and
those not thus projected.
Sanding on the summit of Haleakala one sum-
mer'S day, the heat of tine suns rays fairly hllstered
our hands and faces, while in the shade of the tent
We were chilled with the cold, and ut night the tenn
perature fell TO tie freezing point of water. The
screen of aqueous yapor lies close to the earth; on
the mountain summit, therefore, its density is not
sufficient to temper the heat of the suns rays, or to
intercept the radiation of the heat of the earth,
which gushes freely of into space As soon as the
sun is Withdrawn this loss of heat is shown by the
quick descent of the thermometer and the chill in
the night air.
In those central portions of the continents which
are reached by currents Of air only after they have