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45.

[[image: three dimensional drawing of a long, square "J" shaped tube, the long left branch labeled A D, B across the bottom branch, and C at the top of the  much larger diameter short right branch labeled E at the bottom. HPart way down the left branch is labeled H. Then there are four dotted lines across both branches labeled as follows: N M, G F, I L H E]]

  The same thing will happen if ye brach E C is much more large or much less tan D A: for if you pour mercury till it mounts  to ye height G F, G H ye height of ye mercury  in ye other pipe shall be 28 inches: for as ye mercury D G makes an equilibrium with ye mercury E F, although in a greater quantity, as hath  been proved above in reference to water so ye spring of ye air in F C will make an equilibrium with ye mercury G H since it would sustain it if G H were ofye same largeness as F C and by consequence it makes ye like effect as if ye branch E C was as  heigh as ye other and in it was mercury to ye same height as H.  I have made ye following experiments. having poured Mercury to L wch  was the 3d of E C it was fount 14 inches - 1/4 from above I L in ye other branch, and it will be about 27 inches and 1/2 above G F when ye space E F ye half of E C was full and having raised it to 44 1/2 inches above N M; M C will be bound 3 4/5 and a little more of such parts as E C contains 10; wch makes always ye same proportion: for ye Barometers were then at 27 inches and 1/2: for ye like reasons if ye branch E C was much straighter than ye other, ye air inclosed there would make ye like equilibrium by the spring with ye mercury of ye other branch. we shall see ye same proportions when ye air shall be more rarified than that of ye place whereby experiments is made; wch will be proved after this manner.

  Take a Barometer A B of what lignes you please, as for example of 38 inches, make a mark on a point as Z at an inch above ye open end B, but ye end that that end being plunged in ye mercury of ye small vessel C D E unto that mark, there may remain 37 inches above. Fill ye pipe with mercury and lave 9 inches of air so ye end that when ye pipe shall be reversed as may seen in ye figure and sustained with ye finger, there may be 9 inches of air at ye top of ye pipe; then if you dip ye finger with ye end of ye pipe in ye mercury of ye little vessel and afterwards take away ye finger, ye mercury will descend and will stop after some ballancings at 21 inches, wch ought to happen to preserve ye proportion of ye weights and condensation explained above, and it may be proved in this manner.

Transcription Notes:
mandc: Attn reviewer: "I" looks like author's "J"; "D" looks like author's B. http://echo.mpiwg-berlin.mpg.de/ECHOdocuView?url=/permanent/library/QERNH1MN/pageimg&start=131&viewMode=images&mode=imagepath&pn=174&ww=0.0648&wh=0.2634&wx=0.4716&wy=0.3624