USE OF THE HUMUS. 1 19 



In such a filtering apparatus, built by the hand 

 of nature, we have placed before us experiments 

 which have been continued for a hundred or a 

 thousand years. Now, if water possessed the 

 power of dissolving a hundred-thousandth part 

 of its own weight of humic acid or humate of lime, 

 and humic acid were present, we should find the 

 inner surface of the roofs of these vaults and ca- 

 verns covered with these substances ; but we can- 

 not detect the smallest trace of them. There 

 could scarcely be found a more clear and con- 

 vincing proof of the absence of the humic acid of 

 chemists in common vegetable mould. 



The common view, which has been adopted 

 respecting the modus operandi of humic acid, has 

 given occasion to the following inexplicable phe- 

 nomenon : A very small quantity of humic acid 

 dissolved in water gives it a yellow or brown co- 

 lour. Hence it would be supposed, that a soil 

 would be more fruitful in proportion as it was 

 capable of giving this colour to water, that is, of 

 yielding it humic acid. But it is very remarkable 

 that plants do not thrive in such a soil, and that 

 all manure must have lost this property before it 

 can exercise a favourable influence upon their 

 vegetation. Water from barren peat soils and 

 marshy meadows, upon which few plants flourish, 

 contains much of this humic acid ; but all agricul- 

 turists and gardeners agree that the most suitable 

 and best manure for plants is that which has 



