Page:Philosophical Transactions - Volume 002.djvu/184

 rest; and having drawn out the Air, all the others disappeared, and even the formerly brighter ones shone but faintly, when the Pneumatical Glass seemed to be exhausted. But keeping the included Body a while in that unfriendly place, we perceived the parts, that had retained light, to grow more and more dim, some of them disappearing, and that, which was formerly the most conspicuous, being now but just visible to an attentive Eye, and that scarce without dispute; for if we had not known beforehand, that a shining matter had been included in the Receiver, perhaps we should not have found it out. And he that had the youngest Eyes in the company could not at all discern it, (the Air being let in, the Body began to shine again.) But this being a single Trial, which the lateness of the night hinder'd us from reiterating, is to be further prosecuted, and in differing substances, before much be built upon it.

e Rarefaction or Expansion of the Air having so notable an operation upon our shining Wood, I thought it would not be amiss to try, what the Compression of the Air would do to it. For which purpose we included a piece of it in such a little Instrument to compress, which you may remember to have been devised and proposed by Mr. Hook. But though we impell'd the Air forcibly enough into the Glass, yet by reason of the thickness requisite in such Glasses, and the opacity thence arising, we were not able then to determine, whether or no any change was made in the luminousness of the Wood.

Which I thought the less strange, because by some Experiments purposely devised (at one of which I remember you were present) I had long since observed, That even a great pressure from a fluid Body, which presseth more uniformly against all the parts, it toucheth of the consistent Body, does work a far less manifest change even on soft or tender substances, than one would expect from the force wherewith it compresseth.

And were it nor, that one contrary oftentimes minds us of another, I might have forgot, that I had divers thoughts about finding some good ways of Trying, whether any such change of Texture might be discover'd to be made in the shining Wood by the