MicroGRAPHtAs 
_ From which Experiments, Ithink, we may fafely conclude, thatthe 
Elater of the Air is reciprocal to its extenfion, or at leaft very neer. So 
that to apply it to our prefent purpofe ( which was indeed the chief 
_ caufe of inventing thefe wayes of tryal ) we will fuppofe a Cylinder in- 
_ definitely extended upwards, [I faya Cylinder, not a piece of a Cone, 
_ becaufe, as I may elfewhere fhew in the Explication of Gravity, that tri- 
_ plicate proportion of the fhels of a Sphere, to their refpective diameters, 
I fuppofe to be removed in this cafe by the decreafe of the power of Gra- 
vit} and the preffure of the Air at the bottom of this Cylinder to be 
{trong enough tokeep up a Cylinder of Mercury of thirty inches : Now 
becaufe by the moft accurate tryals of the mott illuftrious and incompa- 
rable Mr. Boyle, publifhed.in his defervedly famous Pneumatick Book, 
the weight of Quickfilver, to that of the Air here below, is found neer 
about as fourteen thoufand toone: If we fuppofe ‘the parts of the Cy- 
linder of the Atmofphere to be every where of an equal denfitv, we thall 
(as he there deduces ) find it extended to the height of thirty five 
thoufand feet, or feven miles: But becaufe by thefe Experiments we have 
fomewhat confirm’d the hypothefis of the reciprocal proportion of the 
Elaters to the Extenfions we fhall find, that by fuppofing this Cylinder of 
the Atmofphere divided into a thoufand parts, eachof which being equi+ 
valent to thirty five feet, or feven geometrical paces,that is,each of thefe 
divifions containing as much Air as is fuppos'd in a Cylinder neer the 
earth of equal diameter,and thirty five foot high, we fhall find the lower- 
moft fo prefs againftthe furface of the Earth with the whole weight of 
the above mentioned thoufand patts; the preflure of the bottomof the 
fecond againft the top of the firft to be 1000 —1 == 999. of the third 
againft the fecond to be 1000 2 998. of the fourth againft the third 
to be’ 1c00 — 3997. of the uppermoft againft the 999. or that next be- 
low it, to be 1coo—999—=1. fo that the extenfion of the lowermoft 
next the Earth, will be tothe extenfion of the next below the upper- 
moft, as 1..to 999. for as the preflure fuftained by the 999. is to the 
preflure faftain'd by the firft, fo isthe extenfion of the firltto the ex- 
tenfion of the 999. fo that, from this hypothetical calculation, we fhall 
find the Air tobe indefinitely extended : Forif we fappofe the whole 
thicknefs of the Air to be divided, as I juft now inftanced, into‘a’thou- 
fand parts, and each of thofe under ‘differing Dimenfions, or Altitudes, 
to contain an equall quantity of Air, we fhall find, that the firlt Cylinder, 
whofe Bafe is fuppd ed to lean on theEarth, willbe found tobe exten 
ded 3523, foots the fecond equal Divifion, or Cylinder, whofe bafis is 
' fuppofed to Jean on the top of the firft,fhall have Its top extended higher 
by 35235 the third 3533? 5 the fourth 35553) cs i os Bere c- 
qual quantity of Air having its dimenfions meafured by 35. and = 
additional number expreft alwayes in the manner of a fraction 5 -wl 
Ww 
whofe denoniinator isalwayesthe preflure of the Atmefphere a d by 
that part, fo that by this means we ‘iay eafily calculate the height of 999- 
may 
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