148 On the Light emitted hj rotten JVood 



the experiments of other observer?, the following differences 

 will be found : 



1st, According to the above experiments, rotten wood 

 does not emit so remarkably clear a light in oxygen gas as 

 Spallanzani observed. The light also was not so speedily ex- 

 tinguished, that is, in scarcely a minute, as found by Tych- 

 sen. And as my observations perfectly coincide with the 

 experiments of 1-Iumboldt and Gartner, Spallanzani's and 

 Tychsen's observations, which I will not venture to doubt, 

 must have been attended with peculiar circumstances. 



2dly, In regard to the diminution of the volume of gas, 

 M. Gartner found it once in oxygen gas two-thirds of the 

 whole. According to my experiments, however, it was,al- 

 wavs much less. 



3dly, The residuum of the oxygen gas, in \\ hich the rotten 

 wood had ceased to be luminous, was found by Gartner, on 

 being subjected to proof, of such a nature that one measure 

 of it mixed with a sufficient quantity of nitrous gas gave 

 a diminution of 207''. I however found the diminution of 

 the residuum in a bell glass to be 120°, and that in another 

 only 21°, though our oxygen gas was prepared from the same 

 material, namely, oxide of manganese, and of a quality 

 equally good. This difference, perhaps, was owing to a dif- 

 ference in the size of the vessels employed, and e\en in the 

 rotten wood. 



4thly, The sudden extinction of phosphorescent wood 

 observed by M.Humboldt in carbonic acid gas purified by 

 means of phosphorus, I did not observe in exceedingly pure 

 gas trusted in the same manner. 



5thly^ M< Humboldt observed the same sudden extinction 

 in azotic gas which had been freed by means of phos- 

 phorus from any oxygen it might contain. But this I was 

 never able to observe, either in azotic gas as pure as possible, 

 or in the same gas exposed to the contact of phosphorus. 



6th! v, In these experiments 1 did not pay very great at- 

 tention to the absorption which might take place of tlie dif-' 

 ferciii kinds of gas, because in researches of this kind in 

 regard to rotten wood no accurate results can be obtained. 

 I bow ever, in general, observed no diminution in the azotic 

 gas; which, on the other hand, according to Tychsen's ob- 

 servations, was greater than that experienced by ox^'gen gas 

 prepared from saltpetre. 



7thly, M. Humboldt found that rotten wood was lu- 

 minous only for a xcvy short time in oil ; whereas Carra- 

 dori's experiments and mine show the contrary. 



8thly, According to M, Gartner, a piece of rotten wood 



continued 



A 



