VOL. II.] PHILOSOPHICAL TRANSACTIONS. 218 



sealed up in a pipe of clear and thin glass; which being carefully done, the 

 wood retained its light very well when the operation was over, and shone for a 

 long time afterwards. 



Exper. 7. On placing a piece of red-hot iron properly within the receiver, 

 and exhausting the air, the operation seemed not to have any effect on it as to 

 alter its shining. 



Exper. 8. Having hermetically sealed up a small piece of shining wood in a 

 slender pipe, and placed it in a small receiver, made of clear glass, it was ex- 

 hausted of air, and afterwards let in again. But by neither of the operations 

 could we perceive any sensible decrement or increase of the light of the wood : 

 which shows that the motion of such bodies as the particles of light may be 

 freely made in vacuo, at least such a vacuum as the engine produces. 



Exper. 9. Taking a cylindrical glass tube sealed at one end, whose bore was 

 about half an inch, and its length a foot or more. Into this pipe near the sealed 

 end was 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 with 

 quicksilver, and put them both into a long receiver; having pumped a while, 

 that the air included in the pipe expanding itself depressed the quicksilver, and so 

 made escapes into the receiver; we then letting 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 the purpose. This done, on 

 plying the pump again, it was observed that as the air in the pipe, by its own 

 spring, expanded itself more and more, and grew thinner and thinner, the 

 shining wood grew dimmer and dimmer, till at length it ceased to shine, the in- 

 ternal air being then got a good way lower than the surface of the external 

 quicksilver : whereupon opening the communication between the cavity of the 

 receiver and the atmosphere, the quicksilver was driven up again, and conse- 

 quently the air above it was restored to its former density, on which the rotten 

 wood also recovered its light. 



Exper. 10. Having taken a stale and shining fish that was almost all over 

 luminous, though much more in the belly and some parts of the head than else- 

 where, and having suspended him in a conveniently shaped receiver, and hav- 

 ing exhausted the receiver as much as usual, it appeared indeed, especially to- 

 wards the latter end of the operation, that the absence of the air considerably 

 lessened, and in some places eclipsed the light of those parts that shone less 

 strongly ; but the belly appeared not much less luminous than before. On re- 

 admitting the air, the light was perceived to be as it were revived and increased, 

 those parts of the fish that were scarce visible before, or shone but dimly, re- 

 ceiving presently their former splendour. 



