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
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