252 Explanation oftkefe Appearances. [Book VI. 



feveral hours. The light was as if gems were fcat- 

 tered over the furface, and continued till the flelh be- 

 gan to putrify, when it vanifhed, which it was believed 

 to do in the form of a crofs. 



The attention of a more philofophic age was diredt- 

 ed to experiments to afcertain the caufe of this light. 

 Mr. Boyle found, that the light of rotten wood was 

 extinguifhed in vacuo, and revived again by the ad- 

 million of air, even after a long continuance in vacuo. 

 The extinction of the light was not fo complete im- ' 

 mediately on exhaufting the receiver, as fome little 

 time afterwards. The wood was not much affected 

 by condenfed air; but the light of a fhining fiih, 

 when put into the condenfing engine, was rendered 

 more vivid by that means. As air is therefore necd- 

 fary to combuflion, thefe experiments clearly indicate, 

 that this light is the effect of a flow combuflion, or 

 ibmething analogous to. it ; and, indeed, the experi- 

 ments upon the phofphorus of Kunkel have fince 

 placed this matter beyond a doubt. The combuftion, 

 however, in thefe cafes, is fo very flow, that no change 

 of air appeared neceflary for the maintenance of this 

 light, for it continued for a long time, even though 

 the wood was confined within a glafs hermetically 

 fealed. 



To explain the caufe of this combuflion it is only 

 neceflary to repeat what has been juft Hated, that there 

 exifts in every animal body, and in mofl vegetables, a 

 certain quantity of phofphorus. This principle, we 

 have feen, is extremely active^ and has the ftrorigeft 

 tendency to unite with the pure part of our common 

 air. During that feparation, therefore, of the parts of 

 bodies, which takes place in an incipient putrefaction,, 

 thefe phofphoric particles are detached from thofe with 

 which they are combined, and by the action of the air, 



a degree 



