392 SELECTIONS FROM ADDRESSES. 



part burns away when heat is applied, the remaining, or min- 

 eral portion of the soil, is called inorganic matter. The organic 

 part, as it becomes air, and disappears by burning, must have 

 been originally made from air. 



In plants we find the same division as in soils, but with one 

 very essential difference. In plants, the inorganic part or ash, 

 is much the smallest, being often not more than one pound in 

 a hundred, while in soils, it constitutes usually more than three- 

 fourths and often nine-tenths, of the whole weight. 



All plants have the power of drawing in from the surround- 

 ing atmosphere through their leaves, the kinds of air necessary 

 to form their organic part. If any say that this is impossible, 

 I would refer them to the air plants, which flourish and grow 

 vigorously in empty pots at any height from the ground. 

 These must draw every thing from the air, as they have no 

 communication whatever with the soil. The inorganic part of 

 plants must of course all come from the soil ; if there be any 

 organic or vegetable matter there, a part of this may also be of 

 service. In case there is little or none, as usual in light sandy 

 soils, then the plant can draw all, or nearly all from the atmo- 

 sphere. A plant then, that requires little ash, or an ash mostly 

 silica, such as the reeds of the Dutch dunes, can grow and 

 flourish where wheat or corn, requiring many substances be- 

 sides silica, and those too in considerable quantity, would not 

 succeed at all. 



Now we can see what takes place in the gradual improve- 

 ment of a soil by these means. Suppose a crop of reeds, or of 

 spurry, to have grown up and ripened, what is the result ? A 

 large quantity of the surrounding atmosphere has in the process 

 of growth been converted into solid vegetable matter. As au- 

 tumn comes on, the water which the stalks and leaves contain 

 while green is gradually evaporated, they become dry, and fall 

 upon the surface, there to decay. This coating thus formed, 

 is a species of top dressing, it is a positive addition to the soil, 

 of solid substance drawn from foreign sources. When genera- 

 tion after generation has been allowed to grow up and die, 

 nothing being removed, a surface soil is gradually formed, 

 which accumulates from year to year ; as may be seen on nearly 



