# Of the Velocity of Air passing into an Exhausted receiver by Denis Papin

```                                Proposition.1.
From this Principle may easily be deduced this Proposition
that of two differing liquor’s driven by the same pressure, that
which is <u>in specie <\u> lighter must ascend higher then that which
is heavier, and their heigth’s will be reciprocally in the same reason as their
specifick gravity’s are. Thus, quick silver being 13 1/2 times heavier
then water, bear’s as much pressure when it’s spring is one foot
<s>high, as wat  <\s> above the spout hole, as water doth when it’s
spring is 13 1/2 foot high, and the heigth to which Mercury shall
ascend will be 13 1/2 times lesser than the heigth to which water
shall be driven by those equall pressures.
Proposition.2.
From the foregoing Proposition another may easily be deduced
<u>viz<\u> that Of differing liquor’s bearing the same pressure
those that are lighter <u>in specie <\u> must acquire a greater
swiftness, and their differing velocity’s are to one another
as the root’s of the specifick gravity’s of the say’d liquors.
For we have seen Prop.1. that the heigth’s to be attain’d are
in the same reason as the specifick gravity’s; Now <u>Galileus,
Hugenius <\u>, and <s>Mr Hally <\s> others have demonstrated that the Velocity’s
of body’s are to one another as the square root’s of the heigth’s
to which they may ascend: and so in this occasion they are also
as the root’s of the specifick gravity’s.
If therefore we will know what is the velocity of the Air
being driven by any degree of pressure whatsoever, we ought
but to find what would be the velocity of water under the
same pressure: and then take the square root’s of the specifick
gravity’s of these two liquor’s, because as much as the square
root of the specifick gravity of water, will exceed the
square root of the specifick gravity of Air, so much in
proportion will the velocity of Air exceed the velocity of
water. For example, when I have computed what should
be the swiftness of a bullet shott by the pneumatick engine,
as hath been described in the Philosophical Transactions,
I should first compute what was the velocity of the Air itself
```
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## Manuscript details

Author
Denis Papin
Reference
CLP/18i/35
Series
Cl.P
Date
1686
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## Cite as

Of the Velocity of Air passing into an Exhausted receiver by Denis Papin, 1686. From The Royal Society, CLP/18i/35