The Cecil Whig. [volume] (Elkton, Md.) 1841-current, 1860-04-28
an 1nterrstlng Ccfturr.
Constituents Of the Atmosphere,

Kew DR. Cahll, n celebrated scientific gen
tleman from Europe, has been delivering a
course CT lectures in Philadelphia the past
week Or two. The following is synopsis Of
one of the course, which we take from The
Inquirer.
Ladies and gentlemen We have n most
important subject Of natural philosophy to
teach namely the motion of winds. 1t
is subject which lies within certain hounda.
,ics and requires my little knowledge of
other branches Of natural philosophy for its
full development. Like all other such qucs.
tions you have. to approach ii by very slow
degrees. | shall en1eavor to advance. by such
reasoning. as to leave nothing in doubt or
mSconcep,ion. Therefore. our first remark
upon the subject Is. that the air we breathe
is called atmosphere, until put in motion, aud
when il is IN motion, we call it wind The
whole subject which intend to propose to
you this evening, is 10 account for the princi,
pie of winds, together with all the natural
phenomena connected with this most impor-
tant subject. But before | proceed, must
take up my propositions, as have been in
the habit Of doing in the discussion Of phos.
optical subjects. / shall first call your at,cn.
tion TO the height of the atmosphere and in
calling your attention to this point have to
say that the atmosphere is a fluid, from
" tluo.' 20 flow.
There are four or five fluids in this room
Light is one fluid, caloric is another fluid -
Every body in this room is filed with caIoric
-calorc in its latent or concentrated state -
Calorlc is the cause of the sensation of heat
but il is not The sensation itself. | hit my head
on this table, ana feel a sensation of pain -
Surely no one would say that the pain is in
the table. Daughter This is To show YOU
that the thing we call sensation has no con-
ncction whatever with the thing that causes
it. ! merely mention the fact 20 show that
they are two distinct things. So the calnric
in this room, or the" heat" as men call il,
Ito avoid the oppresSivcnesS Of pedantry) is
one fluid. The fluid OF electricity is in every
part OF this room now The fluid of gravi,a.
iion is in every part of this room. The fluid
OF air ~ in every part Of this room. Light
calorc gravi:aion, electricity then, are all
fluids. and flow from one place to another.
The atmosphere. besides being a fluid. is
also elastic. because it may be pressed upon
without losing its volume. although that vol
nme may undergo an apparent dimnution.
1T surrounds the earth in bent zone, and is
about fifty five miles high You ask NE how
can tell that? | can tell even though
never leave this city. We have certain prin.
cplcs by which we are aole to ascertain the
length of the atmosphere. without going up
but very short space. Our instruments are
so accurate that we can discover the atmos-
Fhefe hight without leaving this room -
This instrument consists Of q cubical box of
tin. foot wide, a foot long and foot de, D.
We Will station ourselves at the foot Of Mount
Blanc, for the bottom of that mountain is
Abopt L. val W h .bn I, &c, l.,
like the basins of Paris. or artesian wells
where we obtain water about 100 rlcsS. Fab.
rcnheit. The foot of Mount Blanc is abou,
OH level with the superficial curve of the
earth. If yon wanted to measure the height
OF anything. you would not go to the top of
that mountain. No! But you would take
the level Of the sea as your standai of inca
surement.
Well, as have already said, the land at the
base OF this mountain is very nearly level
with the surface of the ocean. We weigh the
contents Of OR box there. with the air in it,
and having done this. we exhaust the air BY
an air'pu'np, and examine the weight Of it
We find the difference is an ounce and quar-
ter, 81 that a cubic foot Of air wpighs | /,
ounces, or 600 grains. go up the side of the
mountain-it is not more than three miles
high at this place and | 60 up a mile per
pendlculally, not obliqucly, and then take
out the air fIom the bog and let in fresh air.
which find is precisely eleven grains lighter
may not be accurate in this statement but
nevertheless the accuracy is sufficient to illus.
trate principle cubic foot of air, there
fore, at the hight of mile weighs eleven
grains less.
This is owing to the fact that the mass of
Dir surrounding the earth presses upon it W it'll
considerable weight, and when YOU ascend a
mile, yon remove mile of the superncum-
bent pressure. Therefore. when this pressure
Of a mile is removed. the upper stratum of air
does not pack into the same space or territory.
and consequently the whole space, although
filled, is filled with lighter air, which weighs
eleven grains less. We 60 up another mile
and We repeat the same experiment, and the
air is twenty-five grains less, not being so
closely packed. If were teaching geometry
or algebra, might be able to tell you, by
either Of those sciences, ficm these facts,
where it was that the air weighs nothing. A
cubic foot of air weighs 600 grains-a mile
up. grains lighter two miles up, % grains
lighter; three miles up. 80 grains lighter. -
Where will the pressure entirely cease g
When we arrive at ffty.fve miles the pres
sure is so thin that it is not appreciate. We
might calculate that, ard wc do calculate it