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We put in a piece of Wood bigger than the former (this being above an inch long) and that shone very vigorously. And having by a few sucks quite deprived it of Light, we left it in the exhausted Receiver for full half an hour, and then coming into the dark Room again, we found all had not continued so stanch, but that some small portion of Air had insinuated it self into the Receiver. This we concluded to be but a small portion of Air, because the Wood was but visible to an attentive Eye. And yet, that it was really some Air, which was got in, that caused the little glimmering light, which we perceived, may appear by this, that it did presently (as was expected) vanish at the first or second suck; and then the Air being let into the dark Receiver, the included Wood presently shone again as before, though I suspected, I discerned some little diminution of its brightness; which yet, 'till further Trials of the like kind, and for a longer time, have been made, I dare not affirm. Before the Receiver was sufficiently emptied at the beginning of the Experiment made with this greater piece of Wood, a small Leak accidentally sprung, which, letting in a little Air, did sooner than we intended, recall the almost disappearing Light.
Experiment IV.
There is an Experiment of affinity with the former, which we thought it not altogether impertinent to try: For having observed on 'another occasion, That sometimes the Operation, which the withdrawing the Air hath upon a Body included in the Receiver, proves more considerable some minutes after we have ceased pumping, than immediately after the exercise is left off, I imagined, that even in such cases, where the Light is not made wholly to disappear (though it be made almost quite to do so) by the emptying of the Pneumatical Glass, the suffering the Body to remain a while there, though without any pumping (unless now and then a very little to remove the Air, that might have stollen in in the mean time) the remaining Light of the Body might probably be further impaired, if not reduced quite to vanish. To examine this conjecture, we put in a Bod that was not Wood, which had some parts much more luminous than the
