The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1868-12-12
TINE BAROMETER AND IT'S USES.


Professor Guyot.
The third OF the winter course Of scientific lectures
before the American Institute was delivered last
evening at Steinway Hall before large and select
audience, q goody proportion OF ladies being pre-
sent. The lecturer, Professor Guyot, OF the College
OF New Jersey Princeton, chose as the subject of his
discourse "The Barometer and illustrated his re-
marks by frequent references to charts diagrams
and philosophical apparatus
The lecturer was introduced by Judge DAILY with q
few highly complimentary remarks, and proceeded
TO say that our earth was composed OF various ele
ments, solid, liquid and gaseous, three different
states of the same matter, which, neverthe-
less, perform very different functions in the
whole system OF the globe, considered as
great Individual. on the land were found by far the
highest forms of life, whether OF animals plants.
It was on the solid ground that man also thriyed,
developed and civilized, and there alone he could
find ali the elements for his work. In the water,
which covered nearly three-fourths OF our globe,
were found nearly all the organisms or az least most
or them, which were characterized by low grade
OF organization. These two in themselves, were
the lower elements; but nevertheless, all knew now
perfectly Indispensable they were for the life of the
higher. The gaseous atmosphere which surrounds
both animals and plants high and low, gives power
to man and all the lower animals for movement, and
1t was from this that we derived all the motive
powers which were In u.s. IL was apparent therefore,
That this third element was by no means unimportant
though II did not furnish the same materials that
were necessary tor our bodies but It furnished the
power OF notion and 1t was with this power that he
would have to do this evening. We summed up
under the name of climate most OF those influences
and those influences spoken of under the general
title OF climate comprised especially the heat or
temperature OF the atmosphere an amount OF water
indispensable to life OF animals and plants, and last
~ weight or density Our subject was confirmed
prominently, though not entirely so, to the IN
vestigation OF the weight OF the atmosphere
by means Of an instrument which we knew as the
barometer. The atmosphere was simply garment
for the whole globe, and apparently very
thin one, since Its height WAS not more
our miles, above the level Of the sea contained more
than half OF the total weight OF the whole atm0s-
phere 1t was IN this very thin layer that the whole
OF animated nature was performing its functions.
The atmosphere Of a globe fifteen feet in diameter
would II proportioned TO the atmosphere surround.
ing earth planet would be to that artificial
CLONE not more than two inches. and q proper
toned part to that in which life ~ developed and
sustained would make but small fraction OF an
inch barometer meant an instrument TO mea-
sure the weight OF the atmosphere and was derived
from two Greek words Until the seventeenth CEN
fury IL was scarcely believed. except by n few
select minds, that the atmosphere had any weight
nj all. Aristotle tried an experiment to determine
whether there was any weight in air or not but
failed in consequence Of making the attempt I'm
properly, and indeed, until the time OF the great
Calico the belief prevailed that the air had no
weight at all, and the conroverson Of that opinion
was due To Calico a. the result OF his discovery.
II while engaged IN the further investigation Of
this discovery that he died leaving TO his disciple,
Torriceli. TO complete his discovery by the inven
tion OF the barometer. The experiments was by
taking tube and filling II win mercury or SUBJ
stance thirty and half times heavier than water
itself and returning this tube In a cup OF mercury.
II was found that the mercury would sink, leaving
space above free from matter, which was vacuum.
so far as q vacuum could exist. The theory was that
the atmosphere pressing upon the mercury In the
cisern would cause tue mercury TO rise In the tube
and the weight Of the air would be expressed by that
column Of mercury. This was the instrument which
demonstraisd 70 all eyes ina, me ar ar, hsa weigh,
air, giving us about fifteen pounds TO the square
inch AZ the weight OF the atmosphere. In order TO
express the conditions which must exist To make a
good barometer and an accurate one ~ might be
well to give idea OF It's construction before pro-
ceedIng any further The simplest form OF a baro-
meter was always the best. 1t had. however, been
improved by the application OF scale which mea
sured the distance between the two surfaces OF ner
curry. When the variations In the barometer takes
place portion of the mercury, II the baro-
meter falls would enter the cup below
nn' you ua'e naa axed scale. that 'e scale
would not measure the difference The scale must
he brought 10 touch the surface below and measure
the surface above. What was called the syphon
barometer could oe substituted for this cstern. IL
had two branches and according TO the same law u
was only necessary to measure from point any
where the height of the mercury IN the principal
branch and the height in the inferior branch. The
difference would be the barometric height The
common barometer WAS the syphoD barometer, In
which the branch had been expanded ia ORDER 10
prevent the rising or falling OF the column inside the
longer branch. The syphon might I've made 10 regis
ter IN q more convenient way by means 81 handle
but the difficulty about this was that the In
struncni's precision WAS impaired by oxidation
rne best Instruments have been male IN America
for USE In observations and for measuring the height
OF nountas, where great accuracy OF nAeasureInent
was indispensable and where the instrument must
be correct even to the housandth part OF IN inch IN
order 10 secure accurate measurement. they were
introduced In this country In 1851, and hud since
been greatly modified, TO fulfil all the vequre-
mcafs OF . barometer. BY means Of This instrument
practiscd observer could vouch for the correctness
OF the reading to the two thousandth part 9f an
inch But FOR the purpose OF determining the attitude
Of mountains there was found 10 be another impor.
iant requisite, which was 10 make an instrument
that would not break II had been f0unp
In several United states governmeat expedi.
t,ois that when the barometer was wanted
for csc 1t was broken. The baroInetric tube
should he kept free from air otherwise IL would pass
mo through the tube and make vast difference.
This was done by boiling, ana a defect could be
easily detected from the fact that the mercury In
CLIMBING lie barometer would pe heard 10 strike