Nov. 1896.] BOTANICAL SOCIETY OF EDINBURGH 11 



It would take me too far to enter into any detail regard- 

 ing chemical processes of that kind, and it is the less 

 necessary because, although they are known to occur, I 

 have no idea of the extent to which they are operating, 

 and I cannot estimate their importance. 



As when organic substances are being consumed by the 

 slow processes of putrefaction and decay, so also when they 

 are being burned a considerable part of the nitrogen is set 

 free as such. The burning of wood and of coal are opera- 

 tions in which a very appreciable amount of uncombined 

 nitrogen is set free. It may be said of coal that its com- 

 bustion is a gain rather than a loss to the available nitrogen 

 of the world, because far more of the nitrogen it contains 

 is set free as ammonia than as nitrogen gas. No doubt 

 that is so, but the nitrogen contained in the coal measures 

 must have been got from the atmosphere at the time when 

 the plants that made the coal were growing, and we can 

 regard the nitrogenous matter locked up in them only as 

 part of the funded capital of the combined nitrogen of the 

 world, and any process of combustion which sets the com- 

 bined nitrogen free is an expenditure of that capital, and 

 it is evident that if the process of spending goes on long 

 enough, there will by and by be no capital of combined 

 nitrogen to draw upon. 



Besides the sources of loss which I have indicated as 

 going on in what may be called dead organic matters, 

 there are others which are known to be going on in the 

 bodies of living animals, — fermentations in which the 

 nitrogen contained in the albuminoid matter of their food 

 is to some extent liberated in the uncombined form. 



It will be seen that the circumstances in which combined 

 nitrogen becomes free are very various, and as we do not 

 know them all, but probably only a few of them, we are 

 forced to conclude that, unless there are some means 

 whereby free nitrogen is brought again into combination, 

 and unless these means are not only active but abundant, 

 we must be hastening on to a time when life in any form 

 upon the globe must become extinct for want of nourish- 

 ment. 



A survey of the history of the globe shows us, however, 

 that life is on the increase, and that organic matter is 



