212 PHILOSOPHICAL TRANSACTIONS. [aNNO 1668. 



afterwards, upon the restitution of air, to recover presently, and show manifest 

 signs of life ; having therefore exhausted the receiver, till the wood quite disap- 

 peared, we stayed above a quarter of an hour in the dark, without perceiving 

 that the wood had regained any thing of light, though about the end of this 

 time we made the place about it as dark as we could ; and then, it being too late 

 at night to protract the experiment, we let in the air, and on the admission the 

 wood presently recovered light enough to be conspicuous at a distance, though 

 it seemed to me somewhat less vivid than before. 



The following night we put in a piece of wood larger than the former, being 

 above an inch long, which shone very bright. And having by a few exhaus- 

 tions quite deprived it of light, we left it in the exhausted receiver for full half 

 an hour, then coming into the dark room again, we found that some small 

 portion of air had insinuated itself into the receiver. 



Exper. 4. Having observed that sometimes the operation, which the with- 

 drawing the air has upon a body included in the receiver, proves more consi- 

 derable some minutes after we have ceased pumping than it is immediately after, 

 I imagined that even in such cases where the light is not made wholly to disap- 

 pear by the emptying of the pneumatical glass, the suffering the body to re- 

 main a while there, though without any pumping, the remaining light of the 

 body might probably be further impaired, if not be made quite to vanish. To 

 examine this conjecture, we put in a body that was not wood, which had some 

 parts much more luminous than the rest ; and having drawn out the air, all the 

 others disappeared, and even the formerly brighter ones shone but faintly, when 

 the receiver seemed to be exhausted. But keeping the included body a while 

 in that situation, 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. The air being 

 let in, the body began to shine again. 



Exper. 5. The rarefaction of the air having so notable an effect on the shin- 

 ing 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 lit- 

 tle instrument to compress, as that devised and proposed by M. Hook. But 

 though we impelled 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. 



Exper. 6. To try whether a small quantity of air, without being renewed, 

 might not suffice to maintain this cold fire, though it will not that of a live 

 coal, or a piece of match, we caused a piece of shining wood to be hermetically 



