29 On the Light emitted ly rotten IVood 



It did not aj^ear that the want of moisture was a principal 

 cause of the cessation of the phosphorescence; for I found 

 the wood often moist in a greater or less degree, and espe- 

 cially when it came in contact with the water by which the 

 mouth of the bell was closed. 



Experiment III, 



I filled several bell glasses with azotic gas as pure as pos- 

 sible, which I had separated from atmospheric air by long 

 continued agitation of an amalgam of lead, or by six months 

 action of a solution of alkaline sulphuret, or by moist gar- 

 den earth, and which tried in an eudiometer mixed with 

 nitrous gas exhibited no diminution. The phosphorescence 

 of the wood in this gas continued at first without any de- 

 crease, and as strong as in oxygen gas ; but after from one 

 to tour hours it became weaker in the different bells : in 

 some it ceased entirely at the end of an hour and a half, in 

 others not till the end of from five to fourteen hours; the 

 cause of which, in all probability, was the unavoidable di- 

 versity in the nature of the pieces of wood. After '24 hours 

 I introduced into several of these bells from half a cubic 

 inch to an inch of fresh azotic gas ; but in neither of these 

 cases was there the least appearance of light. But having 

 introduced, with proper care, a new piece of wood, it emit- 

 ted, in these as well as in the other vessels which had received 

 no mixture of new azotic gas, as strong a light as in at- 

 mospheric air, and continued undiminished for some time. 

 In some of the bells it was not extinguished till the end of 

 2, 4, or 5 hours, though no oxygen gas had been intro- 

 duced. 



Experiment IV. 



I put into some of the bells along with the rotten wood 

 small bits of phosphorus ; and having introduced some of 

 the above azotic gas, the wood and the phosphorus both 

 began to be luminous. At the end of an hour the lumi- 

 nous appearance of the wood was considerably weakened, 

 and it at length decreased so much that its light could no 

 longer be distinguished any more than that of the phos- 

 phorus. At the end of 24 hours, when the light of both 

 substances had already ceased for a considerable time, I in- 

 troduced, with proper caution, a new piece of wood into 

 the gas in which the former still continued luminous. A 

 proof that by this operation no atmospheric air had been 

 mlroduccd was, that the phosphorus remained dark, and 

 I could observe no luminous vapour in the glass. In about 



an. 



