1j^ 'Ontlie Light of J^^aitiyal Phojphor'i. 



The experiment of placing the luminous flies in oxygen is not new. It was teforc 

 made by Forfter; for which fee his Theory of Heat, and the Journal de Rozier for 1784. 

 He obferved that they give much more heat in this fluid, not only at intervals, but con- 

 tinually. M. Forfter moreover aflures us, that he difcovered the organs of refpiration in 

 thofe infe£ls, which M. Spallanzani could not find. He defcribes them precifely, by ob- 

 •ferving that in each of the luminous rings there are two air paflages, furnilhed with val- 

 vules at their apertures, and that thefe paflages are loft in the interior ftrudlurc of the 

 animal. 



I have fecn two fpecies of luccioloni, or fliining worms ; namely, a larger and a fmaller, 

 -of which I have given a flight defcription in my Theory of Heat, where I fpeak of phof- 

 phori. The firft fpecies alfo difl"ers from the fecond in colour ; the former being nearly 

 grey, and the latter nearly black. The firft have much luminous matter in the three laft 

 tings ; and- the others have lefs in the laft ring but one. Thefe may perhaps have been 

 the fpecies obferved by the Naturalift of Pavia. Both fpecies conceal their phofphorus at 

 pleafure with the utmoft facility. They feem therefore to be aware of its effeiSls, parti- 

 cularly the fecond fpecies. 



It is not true, as certain naturalifts, as well as Iil. Spallanzani, pretend, that the lucci- 

 oloni and lucclole are animals of the fame fpecies, difterent only in fcx, that is to fay, that 

 -the former are the males, and die latter the females. I can afllrm that I have feen the luc- 

 ciole pregnant, with the abdomen filled with eggs : and this part, which. before was fo lumi- 

 nous, had its phofphoric part very much diminilhed, being reduced to merely two points, 

 and two fmall lateral portions. The lucciole begin to difappear precifely at the time of 

 their pregnancy, which is the caufe why they conceal themfelves. If they be fought for 

 among the grals and underwood, they are found in this ftate*. 



If it he certain then that phofphoric wood, the luccioloni and the lucciole continue to 

 ihine under oil, it muft be admitted that this light docs not arife from a flow comburtion, 

 as Spallanzani pretends, becaufe oil contains no air to fupport it. This is the legitimate 

 and immediate confequcnce which muft follow from this experiment, and cannot be 

 refufed. The experiments of Spallanzani lead to peculiar confequences, tliough difTerent 

 from thofe he has deduced. It is poffible that the unrefpirable air may aft in a particular 

 manner on thefe phofphori, which may be capable of preventing the emanation of their 

 lights; and that oxygen, by a particular aiSlion of a contrary kind, may augment it. 



Why ftiould it be difputed that the diff'erent airs may produce peculiar effeds on thefe 

 fubftances, with which we are not yet acquainted ? To Spallanzani will be due the honour 

 of firft obferving them. In the fame manner as various fluids are pernicious to natural 

 phofphori, and prevent their fliining, why may not the air produce the fame effeft ? I have 

 found by experiment, that the phofphorus of the lucciole is fuddenly extinguilhed if they 

 be plunged in alcohol, or in vinegar ; but continues to fliine in oil in the fame manner as in 

 water and in air. 



It may be objefted to me, that Spallanzani has made the experiment, that the phofpho- 

 rus of the (hining worms produces a diminution of volume in oxygen gas, at the fame time 



that their light is increafed ; whence it 



) be concluded that the procefs is analogous 



" See the note No. i. p. 7S. torn. n. Jf my Theoiy of Htat. C. 



o to 



