Page:Philosophical Transactions - Volume 002.djvu/189

 clear and conveniently shaped Glass, that the long Stem or Pipe being so far filled with Quicksilver, as that there might be about half a spoonful of Air left at the enclosed end where the Wood was placed, it might be inverted into a little Glass of Stagnant Quicksilver, and therewith conveyed into a slender Receiver, out of which, as the Air should come to be pumped, that included in the Glass, which held the Wood, might be rarified, and afterwards upon the admission of the outward Air (which must impell up the Quicksilver to its former height) might be restored to its former state: But when we came to make trial of this, we had no Receiver conveniently shaped that was so clear and thin, as that we could see the Wood shine through both the Glasses. And though we would for an Expedient have substituted a fine thin Bladder wherein the Wood was to be put, and a convenient quantity of Air strongly tied up with it, yet for want of a Bladder fine enough for our turn, that Expedient also proved useless to us. But being desirous to make what trial we could by the least unfit means we had in our power, we got an old, but thin Glass, sealed at one end, whose shape was pretty Cylindrical, and whole bore was about the bigness of a man's little finger, and whole length was about a foot or more. Into this Pipe, near the seal'd end, we put a piece of Shining Wood, wedged in with a piece of Cork to keep it from falling; and having inverted the nose of it into another slender Glass, but not Cylindrical, wherein was pretty store of Quicksilver, we put them both into a long Receiver, shaped almost like a Glass Churn, and having pumped a while, that the Air included in the Pipe expanding it self, might depress the Quicksilver, and so make escapes into the Receiver as long as we thought fit; we then let in the outward Air, that the stagnant Quicksilver might be impelled into the cavity of the Pipe now freed from much of the Air, to the height requisite for our purpose.

This done, we plied the Pump again, and observed, That as the Air in the Pipe did by its own Spring expand it self more and more, and grow thinner and thinner, the Shining Wood grew dimmer and dimmer, till at length it ceased to shine, the internal Air being then got a good way lower, than the surface of the external Quicksilver; whereupon opening the commerce between the cavity of the Receiver, and the Atmosphere, the silver