THE SOIL 83 



surfaces are rough to the touch, the edges are rounded, there 

 are cracks here and there. Study the face of any cliff, note 

 its great cracks, and see what huge fragments have split off 

 and are lying at the bottom. Look at the stones in a brook : 

 they are rounded, and where they are softest there they are 

 worn away the most. After a rain the brook is cloudy with 

 mud. All these things show the effect of air and water, sun 

 and frost, on the rocks. The sun and the frost crack the 

 stone, water works in, dissolves some of the stone, and, freez- 

 ing, makes the crack wider. Fragments, falling, break 

 against each other; the brook grinds them heavily, and 

 slowly they become smaller and smaller. They are made into 

 sand. 



Where these smaller pieces are thickest is of course the 

 bottoms of slopes and the mouths of rivers, where water has 

 carried them. But to go farther into this takes us into the 

 study of geology. 



Among the small fragments, and in the hollows of the rocks 

 where dust had settled in the cracks, grew the first plants. 

 When they died they decayed, and made food for later plants. 

 The dead matter mixed with the broken rock, and darkened 

 it. This was the beginning of loam. 



Let us study a handful of the loam which we took from the 

 garden. Get a tall, narrow bottle : a stuffed-olive bottle is 

 perfect for the purpose. Into this put two tablespoonfuls of 

 the loam, after you have picked out everything, whether 

 stick or stone, that is big enough to be noticed. Fill the 

 bottle nearly full with water, cork it or stop it with the palm, 

 and shake as vigorously as you can. If at first the earth 

 clings to the bottom, stir it with a stick. Then when the 

 whole is swirling violently, put the bottle down and let the 

 contents settle. Watch it. 



You will notice that almost at once you can see grains, as 



