The Sun.
London, England, 1849-12-10 00:00:00

THE DENSITY.

The law of the decrease of temperature, or, rather, of
density in ascending, is so little known that its hives-
tigation has been expressly recommended by the
British Association. It is thought to be nearly
this :—when the heights increase in arithmetical pro-
gression, the densities decrease in geometrical pro-
gression, so that, if air at seven miles high occupy
four times the space it does on the surface, then, at
fourteen miles high, it would occupy sixteen times
the space, and at twenty-one miles high sixty•four
times, and so on. At this rate, at the height of
forty two miles, it would occupy four thousand
times the space ; but then the cold counteracts this,
and leaves the question to be settled only by experi-
ment. There are reasons to believe that the air
extends at least five hundred miles high in a state cal
pable of maintaining combustion.

OTHER GASES AND COMPOUNDS IN THE ATMOSPHERE.
There is evidence of other constituents of the
atmosphere beyond the boundaries of the air,
properly so called. Hydrogen gas—atnmoniacal
gas, produced by twenty-five of hydrogen and
seventy five of nitrogen, lighter than air ;
phosphorus also may be in the atmosphere, by the
light given out by snow in the night time, and by the
fact of snow falling in Argyleshire in March, 1813,
when the light was so great as to make the bodies on
which the snow fell seem to be on fire. Hence the
possibility of phosphoretted hydrogen gas, which
inflames spontaneously when in contact with air, and
produces water and phosphoric acid, which latter
forms white cloudy rings, which enlarge as they
ascend, &c.
NI. Izard, in his work on " Atmospheric Litho-
logy," published in Paris in 1803, says on this sub-
ject (after remarking on the vast quantities of
hydrogen gas which rise continually into the atmo-
sphere, since it is continually disengaged by the
decomposition of water, and all dead vegetable and
animal substances)—" It appears, then, that if there are
formed in the atmosphere combinations of oxygen and
hydrogen, which produce us water, they are affected
in quite another manner than is generally thought.
Ist. They may be made molecularly, as it were, by
the presence and contact of small globules of hydrogen
spread abroad in the atmosphere while they traverse
it in their way to unite in the superior regions. In
this case the combination takes place without detona-
tion or light, but solely with a change, more or less
sensible, of the temperature of the air, and the water
which results, falls like that which is only aqueous gas
condensed." This accounts for rain without clouds,
&c., mentioned by M. Arago, and is, therefore,
extremely probable.
"2ndly, says M. Izard, " this combination may
take place instantaneously, by the combining of a
great quantity of hydrogen, amassed spherically and
isolated by other neighbouring gases. This is made
with detonation, more or less violent, and produces
hail and heavy rain, which fall rapidly."
" 3rdly. Without the globulous mass of hydrog en
coning immediately into contact with the sphere of
common air, the combination of the two gases,
oxygen and hydrogen, may be determined by a mass
of intermediate fluid, which should have a great
affinity for both those gases. It is this combination
which is ordinarily the effect of the electric fluid ; it
is made with detonation and light, and has nothing in
common with the phenomena produced by the shock
or electricity of clouds, since it often takes place in
stormy climates, when the weather is calm and the
sky serene."
In my opinion the pher.omenoa of " falling stars"
is more satisfactorily accounted for by this latter ex-
planation than by any of the hypotheses at present
known.

The above "Notes on Met4orology" are offered to
the society with a view to remind the student in this
science of the many salient and very beautiful points
it offers to his attention, and as an inducement to its
better study and appreciation.