COMPOSITION OF SOILS 



309 



soils are made up almost entirely of decayed vegetable matter, 

 peat, and muck. The underlying coarser and lighter colored 

 soil, which contains little if any vegetable matter, is usually 

 called the subsoil. 



Composition of Soils. Experiment 89. Examine under a 

 strong magnifying glass samples of sand, loam, clay, peat, and other 

 kinds of soil. Notice the differ- 

 ent kinds of particles composing 

 the different soils and the shapes 

 of these particles. 



Experiment 90. Put a hand- 

 ful of ordinary loamy soil into a 

 fruit jar nearly full of water and 

 allow it to stand for a day or two, 

 shaking occasionally. At the end 

 of this time shake very thoroughly 

 and after allowing it to settle for 

 a minute, pour off the muddy 

 water into another jar. Allow 

 this to stand for about an hour 

 and then pour off the roily water 

 and evaporate it slowly, being 

 careful not to burn the material 

 left. Examine with the eye, by 

 rubbing between the thumb and 



fingers, and with a magnifying glass, the three substances thus 

 separated. These three separates will be composed largely of 

 sand, silt, and clay. 



If a compound microscope (Figure 93) is available, mix a bit of 

 the silt and of the clay in drops of water and put these drops on 

 glass slides. Examine the drops under the low power of the micro- 

 scope. Notice the little black particles of decayed vegetable mat- 

 ter, also the little bunches of particles that may still cling together. 

 Why was it necessary to soak the soil so long? Draw the shapes 

 of a few of the particles. Describe the composition of the soil you 

 have examined. 



FIGURE 93 



