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natural Cause of the Proposition is this ; that the hot Particles of the Sun's Rays, or any Fire, are

the

greater plenty with the Air Siphon was full of common Air, nearest us, than in the upper and exposed to the external Air Air. These things being laid coming into the Siphon. The down, it is manifest that the Globe and Siphon was plunged Air of the higher Countries be- into hot Water, found by preing less stored with Vapours, vious Experiments to be of the has, in proportion to it's Densi- same degree of Heat as boiling ty, more Elasticity in it thanthat Water, and consequently cauwhich comes next to the Earth, fing the same degree of Rare. whence the reciprocal Ratio of faction ; tho' the Fire underGravity, which is in the Air neath were greater or less. next the Earth, does not hold When the Air included in here; and further, that Va- the Globe was rarefied with pours and Exhalations have not this degree of Heat, it would such Elasticity as Air, but that be gradually thrust out at the this is much more rarefied and other end of the Siphon ; 'till extenuated. But the excellent at length the Globe being heatMr Fontenelle, Secretary of ed to the utmost, there was the Society, explains these left a very small quantity of Air, Phænomena in a quite diffe- highly rarefied, that pofleffed rent Manner, in his History the whole Cavity. Then the of the Academy, Anno 1708. Water being removed from the

He proposes some Experi- Fire, the Air, as it gradually ments performed by the famous cooled, which before poffefled Mr De la Hire, and others, the whole Globe, being grafrom which he infers, that the dually contracted by the Cold, elaitic Force of the Air is in- gave way to the Water that creased when it is mixed with entered at the Orifice of the Moisture, or when compound- external Leg, and at length, ed of Air and aqueous Vapours, when the Water became entirethe Rarefaction will be greater, ly cold, it was contracted into than from pure Air; and that a very small Space, whilst the therefore on the Tops of Moun- rest of the Globe remained tains the Air is found more filled with Water. Now by rarefied, because many Vapours comparing the Space, poffeffed are carried thither for produ- by the Air, cooled and reducing of Rain. The Experiments ced to it's natural State, and are these:

the whole Cavity of the Globe They took a slender glass Sin which it had at the utmost phon, one of whose Legs end- Heat, it appears how much the ed in a large hollow Sphere, be- Air was rarefied with that des ing open at the other. This grce of Heat.

This

the most fubtile in the World, and inconstant Motion, and while these are mixed with the At

mosphere,

This Experiment was first Whence it might seem, that the made in clear Weather, again quantity of Air which rarefied in a moist and rainy Season; and with the same degree of Heat at a third time, a little Water poffefred the whole Cavity, was was left adhering to the inner less in the two later, than in Surface of the Globe. And it the former Case; and therefore was observed that the Air con · more dilated, so as to pofless densed at the end of the Ex: the whole Space. periment, in the first Case pos- Again, allowing that the sessed of the Globe, in the Air was more rarefied in the second possessed butą, and in later Cases, yet as this was efthe third 5. Whence Mr fected by the means of Heat, Fontenelle concludes, that the I do not see how it follows Air was more dilated in the that because the Vapours mixed second Case, but particularly in with the Air, and agitated by the third, than in the first Case; Heat, are more rarefied than and therefore as the Air is the Air without Vapours, therefore more dilated the more moist these Vapours without Heat, Vapour is mixed with it ; hence should have a greater Elasticity he concludes it probable, that than pure Air. for the fame Reason, there is a We shall here add a Table 1 greater Rarefactionon the Tops of M. Cassini, junior, made of Mountains, because the Air from the foregoing Observatithat surrounds them is mixed ons, and exhibiting the Height with a greater quantity of Va- of the Air from the Surface of pour. But there are two Con- the Sea, corresponding to the fiderations that render the Ar- Sinkings of the Barometer ; as gument inconclusive. For first also the Spaces increasing in in the two later Experiments, arithmetical Proportion, whereas aqueous Vapours were plen- in the Height of the Air intifully mixed with the Air, it creases almost half a French might happen that when the League, whilst the Barometer Air was condensed, and the finks in twelfths of an Inch, Water entered thro' the Siphon at a time when, being placed into the Globe, these Vapours on the Surface of the Sea, it might again return to Wa- ftands at about 28 French Inches ter, and mixing with the other or 291} of Engliß. I use the Water partly by the Force of French Measures, being unwilCondensation, and partly by ling, by reducing them to the the mutual Attraction there is English Feet, to disturb the

betwixt the Particles of Liquors, beautiful Series of Propor· leave but little true Air inclu- tions by small fractional Parts ; ded in the very small Space. tho' these may, by the help of

the

mosphere, they separate them, with great Force, and so make more Pores, and these fiery Particles going away, the Particles of Air left by themselves,

do

the lefser Table subjoined be easily reduced to English Measure.

Divisions answering Height of the Air. Barometer falling. I to each twelfth | above the Sea':|

of an Inch. Surface. Twelfths of Inch. an Inch. Fathoms. Feet. Fathoms.

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109
121
133

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I 2
12

145 157 170

12

182

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Divisions answering Height of the Air, Barometer falling to each twelfth | above the Sea's

of an Inch.

Surface.. Twelfths of 1 Incb. an Inch.' Fathoms. Feet. Fathoms. Feet.

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| Divisions answering Height of the Air, Barometer falling to each twelfıb above the Sea's of an Inch.

Surface.
Twelfths of
Inch. an Inch. Fathoms. Feet. Fatboms.

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