EA'penmenls on the "Noctiluca mWiaris. 417 



the glow-worm, this matter being separated from the entire 

 insect, it was found by Matteucci to retain its luminous pro- 

 perty for thirty or forty minutes after it was placed in pure 

 hydrogen or carbonic acid gas. Here then we have the phos- 

 phorescence continued much longer than in the case of the 

 barometric vacuum; and where, it may be asked, was the 

 supply of oxygen that maintained the combustion above half 

 an hour in this instance, or how can this fact be reconciled 

 with the statement formerly cited, " that the light ceases to 

 be produced when this gas (oxygen) is not present?" In re- 

 ference to the same point, I may here advert to the increase 

 of light from the effect of carbonic acid on the Noctilucae for- 

 merly described, and may quote also an experiment from the 

 observations of Macartney, in which he states, " Some of the 

 scintillating and hemispherical species of Medusa, contained 

 in a small glass jar, were introduced into the receiver of an 

 air-pump, and the air being exhausted, they shone as usual 

 when shaken; if any difference could be perceived, the light 

 was more easily excited, and continued longer in vacuum*." 



A consideration of these and some similar facts would tend 

 rather to the conclusion drawn by Carradori in reference to 

 the experiments of Forster formerly quoted, on which it is 

 remarked, in the 2nd vol. of Tilloch's Magazine, " The ob- 

 servation made by Forster, that the Luciole diffused a more 

 vivid light in oxygen gas than in atmospheric air, does not, 

 according to Carradori, depend upon a combustion more ani- 

 mated by the inspiration of this gas, but on the animals feel- 

 ing themselves, while in this gas, in a better condition ; " — a 

 conclusion, which seems to furnish a view of the question of 

 sufficient importance, to say the least of it, to merit some no- 

 tice. On the other hand, the instance of the detached lumi- 

 nous segments placed under oxygen, and appearing to absorb 

 a portion of the gas, lends weight to the opinion of Matteucci. 

 It appears, however, by no means certain, even in this case, 

 that the oxygen found to be absorbed, had actually entered 

 into combination with those particles only which are imme- 

 diately concerned in the production of light; it may, on the 

 contrary, be supposed to have been absorbed also, if not prin- 

 cipally, by the other constituents of the organic matter with 

 which the immediate light-emitting particles are combined. 

 And this brings us now to the consideration in the next place 

 of the 



Chemical Nature of the Phosphoresce7it Matter. — In the 

 earlier inquiries respecting the proximate cause of vital phos- 

 phorescence, we find that the actual presence of phosphorus 

 • Phil. Trans. 1810, part 1. p. 285. 



PhiL Mag. S. 3. Vol. 35. No. 238. Dec. 1849. 2 E 



