Of the' Air-Pump. r

gets up into the syringe ; and the spring of theqn-dilated air in, the receiver acting upon thehirface of the quicksilver in the jar, will forcePart of it up into the tube : for the quicksilver’will follow the piston in the syringe, in the same^Y, and for the same reason, that water follows5 he piston of a common .pump when it is raised! n the pump barrel-, and this, according to some,

1S done by suction. But to refute that erroneousnot ’-on, let the air be pumped out of the receiver^•8, and then ail the quicksilver in the tube will■tdl down by its own weight into the jar; andcan-k°t be again raised one hair’s breadth in the tube,y working the syringe: which shews that suc-tlo n had no hand in raising the quicksilver; and,t° prove that it is done by pressure, let the air] nto the receiver by the cock k (fig. I.),and itsAction upon the surface of the quicksilver in thejar will raise it up into the tube, although thepiston of the syringe continues motionless.—Ifthe tube be about 32 or 33 inches high, thequicksilver will rife in it very near as high as itstands at that time in the barometer. And, if*he syringe has a small hole, as m, near the topst, and the piston be drawn up above that hole,

. ^ air will rusti through the hole into the fy-*?. n S e and tube, and the quicksilver will imme-diately fast down into the jar. If this part of theapparatus be air-tight, the quicksilver may bePumped up into the tube to the fame height thatstands in the barometer; but it will go noqjgher, because then the weight of the column in. e tu ke is the fame as the weight of a column ofthe fame thickness with the quicksilver,11 c * teaching from the earth to the top of theatmosphere.

7. Having

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