373 



it was attended by no sensible absorption of ox- 

 ygen. The wood and roots of the mangrove 

 placed under water were exposed to the rays of 

 the Sun. I tried to imitate the daily operations 

 of nature on the coasts at the rise of the tide. 

 Bubbles of air were disengaged, and at the end 

 of ten days formed a volume of thirty-three 

 cubic inches. They were a mixture of azot 

 gas and carbonic acid. Nitrous gas scarce- 

 ly indicated the presence of oxygen *. Lastly, 

 I set the wood and the roots of the mangrove 

 thoroughly wetted, to act on a given volume of 

 atmospheric air in a phial with a ground glass 

 stopple. The whole of the oxygen disappeared ; 

 and, far from being replaced by carbonic acid, 

 limewater indicated only 0 02. There was even 

 a diminution of the volume of air, more than 

 corresponded with the oxygen absorbed. These 

 slight experiments led me to think, that it is 

 the moistened bark and wood, that act upon the 

 atmosphere in the forests of mangrove-trees, and 

 not the water strongly tinged with yellow, 

 which formed a distinct band along the coasts. 

 In pursuing the different stages of decomposi- 

 tion of the ligneous matter, I observed no ap- 

 pearance of a disengagement of sulphuretted 



* In a hundred parts there were eighty-four of nitrogen, 

 fifteen of carbonic acid gas that the water had not absorbed^ 

 and one of oxygen. 



