43 



and 32 Ibs. of nitrogen ; and, \yith proper irrigar 

 tion and a fair soil, even greater results may be 

 obtained. Whence, then, do the plants derive all 

 this carbon and nitrogen ? Not from the soil for 

 meadow soils have been analyzed and found not to 

 contain a single year's supply of carbon in humus ; 

 no vegetable or animal manure is ever used ; and 

 yet year after year undiminishing quantities of 

 carbon and nitrogen are taken away, and the 

 humus, or decaying vegetable matter in the soil, 

 is increasing instead of decreasing. It is therefore 

 evident that these substances must have been 

 derived from some other source than the soil a 

 conclusion which of course is diametrically opposed 

 to the Humus Theory. 



Soils have been subjected to a red heat in order 

 to expel every trace of decaying organic matter, and, 

 when cooled down, were sown with various seeds, 

 which germinated and grew plants as luxuriantly 

 as possible, arriving at complete perfection in all 

 their organs. There is thus not a shadow of 

 a doubt left that the atmospheric air is the principal 

 and primary source of carbon and nitrogen. 



Our early philosophers apparently noticed the 

 more than ordinary fertility of a soil rich in humus, 

 rich in decaying vegetable matter ; but were led to 

 form wrong conclusions on the cause of this ferti- 

 lity. The fact that the presence of humus in a 

 soil tends to a most luxuriant growth of plants is 



