264 TRANSACTIONS OF THE 



pores, consisting of large ones, wliich may be seen between the particles of 

 earth, and the small ones, which occur by themselves ; while the large 

 pores form canals between themselves, the small ones have no direct con- 

 nection with the pore sof the encircling particles. The effect is, as you 

 perceive in figure 1, that the pores and canals are all perfectly empty, the 

 soil being dry, and consequently permitting the canals to communicate at 

 the surface with the air, and thus filling them with it. In this condition 

 you observe the seed c, which is abundantly supplied with air, but no 

 moisture, consequently it cannot grow. 



In figure 2, you will notice that both canals and pores are filled with 

 water, which has completely taken the place of atmospheric air, and the 

 soil may justly be denominated wet, the seed is therefore thoroughly sup- 

 plied with water, but no air, consequently it cannot germinate. This never 

 exactly occurs, for the reason that water dissolves air, to some extent, and 

 the seed does germinate under certain circumstances, but not by any means 

 so advantageously as it would if the soil was in a better condition. 



Figure 3 presents a very different state of soil. The canals, being open, 

 are admirably supplied with air, while, at the same time, the pores are 

 completely filled with water. The seed «, therefore, has sufficient air from 

 the canals, and an abundant supply of water, as every particle of soil com- 

 ing in contact with it abounds with this necessary quality. This may then 

 be considered the exact condition of soil requisite for every period of the 

 plant's growth, and invariably occurs when the soil is merely moist, but 

 not wet, and when it presents the appearance of being well watered, and 

 will still crumble in the hand without attaching particles to it. 



Figure 4 presents for your consideration another condition of a healthy 

 soil, as far as water is concerned, as it is moist, but not wet, the pores only 

 being supplied with water. Still there are only a few canals, the soil hav- 

 ing adhered together, and so shut out the interstitial canals that they pre- 

 sent the appearance of pores. This may be termed an uncultivated clod, 

 into which the roots of plants are incapable of extending their fibres. 



I will now apply the four conditions of soil represented to you, practi- 

 cally, so that you may ascertain when they occur on your farms, and how 

 to obviate them. 



The first condition, then, generally occurs in coarse sand, which contains 

 few pores, and wide canals, owing to the large size of individual particles, 

 which allows a free circulation of air, and cjnsequent dryness. In this case 

 I would permit all the stones found on the surface to remain, as they retain 

 evaporation by casting shades. 



Figure 2 represents a condition of soil that occurs much more frequently 

 in nature, than figure 1, When a quantity of water is added to a dry soil, 

 it immediately fills the interstitial canals, and then enters the pores of each 

 individual particle, which if the supply is not excessive, soon empty the 

 canals, and thus form a perfectly healthy condition of soil. If the supply 

 of water is very great through the medium of a spring, or otherwise, the 



