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

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                                A Demonstration of the Velocity wherwith the Air rushes 
into an Exhausted Receiver lately produced before the R.Society by 
Dr. D. Papin Reg. Soc. S.
There being severall occasions wherein it would be usefull to 
Know the velocity of the Air according to the severall pressures 
that may drive it: the Royall Academy at Paris hath attemp 
ted by some tryalls to attain that Knowledge and by means 
of a bladder which they did some times fill up with water 
and some times with Air; they found that (although the 
weight to squeeze out these liquors, and the hole to let them 
out were the same) nevertheless the bladder when full 
of Air, could be empty’d in the 25th part of the time that 
was required to squeeze out the water out of the same bladder:
from thence they concluded that the swifteness of the Air 
is 25 times greater then that of water when both these 
liquor’s bear the same pressure. This experiment was very 
well thought on, and might serve <s>whilst people should look 
for some thing better <\s> till a better should be 
found out but, sure, these gentlemen knew well enough that this was not perfect: the reason is that 
the Air yieldeth much and so the bladder being fill’d with it,
will become pretty flatt, as soon as a considerable weight is 
lay’d upon it: it is plain therefore that the weight bearing upon 
a large space doth not press every part with the same force 
as it would do if the bladder did for a while remain plump 
as it doth when full of water: more over, the water itself being 
heavy in the bladder mak’s some pressure: so that it appears 
that the pressure in this experiment was not quite so great 
upon the Air as upon the water: I have therefore thought of 
another way which I think better, to come to the say’d knowledge 
and I do humbly submit it to the R. Society.
My way is grounded upon this <u>Hydrostatical Principle <\u>, that 
<u>liquors have a strength to ascend as high as their <s>Spring <\s> source is <\u>
and although the resistence of the <u>Medium <\u> doth always hinder 
<s>the Jettes <\s> Jects d’eau in the open Air from reaching quite so high, nevertheless 
the liquor at its first spouting out, hath the necessary swift 
ness to come to that heigth.

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Denis Papin
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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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