Year: 1863

Among ihe ancient philosophers hypothesis
prevailed that nature aJhorred Z vacuum -
They were Led TO Ills conclusion by observing
that no vacuum existed in the world They
found that when tube was placed with enc
end in the water and tie mouth applied to il
at the other ead. the water would rise in the
tube BY wha; is called suc;ioa-a term still IN
use. but now better understood. From this it
was CONCLUDED that nature abhoTrcd . vacuum.


This Illusion was dispelled by the erection
Of pump at Florence, by which it was found
impossble 10 raise the water 10 the top OF the
pipe Asiouishmeat was excited by the fact,
and Calico being then alive, he was consulted
as to the cause. Upon measuring the hight Of
the tube ii was found 10 be thiFtyfour feet,
bat be could no; explain the phenomenon
Torricelh, his illustrious pupil, uuravelled the
mystery. Up till that period it was supposed
that the air possessed no weight Torricelh
came to the conclusion that it did possess
weight and he inferred that as column Of
water had been raised by suction in a tube TO
the hight of thirty-three feet, if this were due
to the weight aud pressure Of the atmosphere,
it coud in like manner support shorter col
umn OF heavier fuii than water. As mercu-
ry was known to be nearly fourteen times
heavier than water. he said the atmosphere
should support column of mercury about two
aud half feet in hight. In order TO test this
hypothesis he took a glass tube about three
feet in length, closed it at one end and filed it
full of mercury. He then closed lis opened
end with his finger, and set it in basin of
mercury. On Withdrawing his finger the mer
cury fell six inches in the tube, leaving 4 col
umn Of thirty inches standing above the level
of the basin The upper six inches IN the tube
formed perfect vacuum, which, in honor Of
the Inventor, has beeen called the TorricelIian
vacuum" The cause of the suspension of the
mercury in the tube was demonstrated still
more clearly by carrying the apparatus 10 the
top of lofty tower, when the mercury fell two
inches. Thus was disproyed the old hypothe-
sis, mature abhors vacuum" and thus the
barometer was discovered No such principle
as suction exists; it is the pressure of the at
mosphere. not suction, that causes the water
to rise in the inlet tube of pump. Pascal
first proposed and used the barometer TO esti-
mate the hight Of mountains instead of by di-
rect measurement, as had been the method
formerly. This instrument is now exclusively
employed for such purposes.


The velocity Of gases and liquids flowing in
to vacuum is in proportion 10 their pressure
and density, and the pressure Of water and air
is according to the hight Of the column. Thus
a column of water thirty-three feet in hight
exercises a pressure of fifteen pounds on the
square inch, which is exactly the pressure ex.
ercised by column of air ex ending to the
hight Of the atmosphere. The atmosphere in
creases in rarity as we ascend, because air is
compressible; bat water is considered incom-
preside, and on the top of the highest noun
tain il is as dense as at the level of the sea-
Air flows into vacuum at the velocity of one
thousand three hundred and forty feet per sec
ond water from hight of thirty-three feet
the same pressure as the atmosphere-1ows
into vacuum at the velocity Of about forty
six feet per second.