262 BOARD OF AGRICULTURE. 



comes in contact with particles of the soil, which are cooler than 

 the air. 



The power of the soil to absorb raaniirial substances is greatly 

 increased by being thus deepened by drainage. The farmer 

 need not have the least fear that his manure will leach down 

 through the soil thus drained. Two vessels, with holes in the 

 bottom, may be filled, one with a common soil, the other with 

 pure sand ; a given amount of liquid manure from tlie barnyard 

 may be poured upon each of them, and, as it' passes off through 

 the holes in the bottom, that through the pure sand will be 

 found to retain its color and odor, while that passing through 

 common soil will have lost completely its color and odor, being 

 nearly as pure as spring water. 



In whatever manner manurial substances come in contact 

 with soils in good condition, their gases will be immediately 

 absorbed and held by it firmly against any power to separate 

 them, except the growing roots of plants. 



Manurial gases are constantly floating in the air. It is tlius 

 apparent that the soil which is in the best condition, or has in 

 its composition the most carbon or vegetable matter, will gain 

 most from the gases which, to a greater or less degree, fill the 

 air. Thus we see that nature will help most the farmer who 

 does most to help himself. 



These facts will appear more important when we consider that 

 nine-tenths, and often ninety-nine one-hundredths of the dry 

 weight of plants will become aeriform by decay and combustion, 

 leaving but one-tenth, or less, of ashes or earthy matter. 



Though not a particle of this matter is lost, yet the farmer 

 will save most to himself who manages to have most of this 

 decay or combustion take place in his manure heap, being well 

 protected by absorbents, or what is better, within the soil. 



The mechanical preparation of the soil by draining, pulver- 

 ization and aeration, the wonderful power of the soil to absorb 

 and retain plant-food, and some of the resources of tliis food, 

 have been considered. 



A few of the many other substances adding to or necessary to 

 the fertility of tlie soil, their availability to the farmer, and 

 their nature and action, will now be noticed. 



A large part of plant-food is known under the name of ammo- 

 nia or hartshorn. Its detection by the sense of smell is but the 



