Miscellaneous. 



447 



this by the habits of civilization. He has cultivated in the place of 

 forests plants requiring a large supply of nitrogen. This nitrogen he is 

 peculiarly fitted to supply them with, from the effete matter discharged 

 by him. The air contains much more ammonia than is necessary for 

 the purposes of wild plants ; he abstracts out of its superabundance, 

 and merely concentrates it at particular spots, where it meets with 

 plants which peculiarly require it, but none of it is lost to vegetation. 

 The peculiar habits of civilized life cause him to return to the air car- 

 bonic acid, amply compensating for that abstracted by his increase. Tn 

 the form of coal he digs from the earth, and returns to the air the car- 

 bonic acid of former times. The great stream of air which, by the revo- 

 lution of the earth moves from the equator to the poles, wafts in its re- 

 turn this food to tropical climates, where nature yet revels in all her 

 wildness. The food thus sent is immediately appropriated by a luxuri- 

 ant vegetation, and oxygen of course emitted, which the same stream of 

 air, in its progress towards us brings back to supply that consumed 

 in the formation of the food. Thus man, by the habits of civilisation 

 fully compensates for that which he retains by his own increase, 

 and that of the animals dependant upon him. Upon the compen- 

 sation of ammonia, I have almost said enough. The plants of for- 

 mer ages were not such as to require much nitrogen ; hence, 

 although the decrease of carbonic acid from the air was great, that 

 of ammonia was insignificant. The greatest exhausting cause in 

 operation would be the rain which carried it to the sea, and caused 

 it to remain there ; that falling on the land would again evaporate. 

 And though the increase of animal life may, as we have already said, 

 remove for a time the superabundance, this will finally benefit vege- 

 tation. But all this time I have been silent regarding volcanic 

 agencies. I have been so, because I consider them merely as an 

 auxiliary means of furnishing to the air the carbonic acid and oxygen 

 retained by animals during life ; but by no means as being the pri- 

 mary sources of food. 



I would 1 could dwell longer upon these subjects : they are of 

 too extensive a nature to be embraced in a single lecture ; but for 

 you I have been already far too long. My end will be gained if some 

 of you have been convinced that the grand causes formerly in operation 

 for the destruction of animal life have ceased, and that man is not liable 

 to the destructive agencies of former times — if you are convinced that 

 by wonderfully wise plans of Providence, the grand medium of animal 

 and vegetable life, the atmosphere, has become fitted for the recep- 

 tion of man, and attained a state of repose and perfect equilibrium, 



