On th Light of Natural Phofphori, yjj 



ta combudion. But this confequence is -not certain. How many fubftances arc there 

 which have the property by their emanations of altering vital air, in the fame manner as 

 combuftion, which nevertTielefs do not burn nor emit light? The fame may be the cafe 

 with the phofphoric matter of thefe infe£ls. 



There is not a pcrfefil analogy, as Spallanzani pretends, between the phofphori he ha« 

 obferved and the urinous phofphorus, becaufe the latter does not (liinebut at a certain heat ; 

 whereas the natural phofphori fhine at any temperature whatever, provided it be not fo 

 great as to alter their fubftance. This proves, in my opinion, that the light is not an effect 

 of combuftion ; for every combuftion requires a more or lefs elevated degree of heat. 



With regard to the explanation given by Spallanzani of the change of wood into the 

 luminous matter, which fuppofes that the hydrogen and carbon, being fet at liberty, attract 

 oxygen ; I will venture to fay, on the ftrength of my experiments, that it is not probable. 

 It is certain (for I have obferved it myfelf, and probably fome others before me), that 

 wood, when luminous, has almoft totally loft its refmous part, and that confequently in that 

 ftate it retains fcarcely any either of the carbonic or hydrogenous principle*, to which its. 

 combuftibility was owing. And in fa£l, fuch wood as has become luminous is with dif- 

 ficulty burned in the fire, and produces no flame, as every one may try. Indeed it cannot 

 be otherwifc; for the progrefs of putrefailion, which reduces it to that ftate, muft have 

 deprived it of mu(ii of its component parts ; particularly the moft volatile, fuch as hydro- 

 gen. Befides which, as I obferved fome months ago to Brugnatelli, I think very? 

 differently from Spallanzani with regard to the conftitution of thefe fubftances ; namely,. 

 <hat they become phofphorefcent in proportion as they have loft their inflammable prinr 

 ciple, and that the property of abforbing and retaining the light depends on that circurti- 

 ilance. 



My opinion may be extended, in preference to that of Spallanzani, to the eaufe of the 

 phofphoric property of animals ; for it is more reafonable : becaufe we cannot imagine 

 that their luminous matter is either refinous or oily, and confequently is not inflammable j, 

 neither can it contain mud carbon or hydrogen. See my Memoirc on the Lucciole, Anu. 

 Chim. et Hiftoriques de Pavle, tom. xiii. 



If the lucciole ftiine beneath the water, as Spallanzani maintains, becaufe the oxygen gas 

 contained in water ferves to maintain their combuftion, why does not the phofphorus of 

 Kunckel alfo ftiine beneath that fluid l It was llkewife neeeflary to have exhibited fome 

 experiments in fupport of that opinion ; as for example, to have fhewn that the phof- 

 phorus of thofe animals alters or abforbs the vital air contained (uncombined) in water, 

 and that water which does not contain it is not capable of caufing them to fhine. 

 Paviay 



utpril 1$, 1797. 



* Of \yliat principles, then, it this vegetable refidue compofcd ? N.- 



yii. situk 



