472 History of Luminescence 



The " uncertain shining of Fishes " mystified Boyle as it did many 

 others after him. 



At this time Boyle preferred not to comment on the experiments 

 and was willing merely to remark: 



That notwithstanding the Coldness (at least to sense) of Fishes and 

 other animals, there may be in the Heart and Blood a Vital Kind of Fire, 

 which needs Air, as well as those Fires that are sensibly hot: which may 

 lessen the wonder, that Animals should not be able to live when robbed 

 of Air. And if I had now time, I could possibly furnish you with some 

 other Trials, that seem much to favour the Comparison, though as to the 

 opinion it self of a Vital Flame, I shall not now tell you my thoughts 

 about it. 



Boyle's most quoted experiments were carried out with phospho- 

 rescent wood on October 29, 1667, using his air pump: ^^ 



Exp. I: Having at length procured a Piece of shijjiyig Wood, about 

 the bigness of a groat or less, that gave a vivid Light, (for rotten Wood) 

 we put it into a middle size Receiver, so as it was kept from touching 

 the Cement; and the pump being set a-work, we observed not, during the 

 five or six first Exsuctions of the Air, that the splendor of the included 

 Wood was manifestly lessened (though it was never at all increased;) 

 but about the seventh Suck, it seemed to glow a little more dim, and 

 afterwards answered our Expectation, by losing of its Light more and 

 more, as the Air was still farther pumped out; till at length about the 

 tenth Exsuction, (though by the removal of the Candles out of the 

 Room, and by black Cloaths and Hats we made the place as dark as we 

 could, yet) we could not perceive any light at all to proceed from the 

 Wood. 



Exp. IL Wherefore we let in the outward Air by Degrees and had the 

 pleasure to see the seemingly extinguished Light revive so fast and per- 

 fectly, that it looked to us almost like a little Flash of Lightning, and 

 the Splendor of the Wood seemed rather greater than at all less, than 

 before it was put into the Receiver.'^'' 



If a glowing stump is chopped with an axe the chips are lumi- 

 nous throughout and look like so many glowing coals. Boyle was 

 impressed with the similarity of the light-giving process in glow- 

 ing coal and shining wood, as he draws a comparison between the 

 two which brings out the fundamental similarity of combustion 

 processes. This comparison may also serve to summarize his many 

 experiments: ^^ 



Resemblances: 



VII. The Things wherein I observed a Piece of shining Wood and a 

 burning Coal to agree or resemble each other are principally these five: 



" Works of Boyle 3: 170-174, 2nd ed., 1772, based on Phil. Trans. 2: 605-612. 1668. 



