EXERCISE III. 

 SOIL. 



Supplies for a Laboratory Section of Twelve. A quart or more of air-dry coarse sand: air-dry pulverized 

 silt loam; air-dry pulverized clay; muck; a few clods of ordinary soil; three teaspoons; one compound micro- 

 scope; thirty-six test tubes; thirty-six evaporating dishes; twelve glass stirring rods; twelve pieces of some 

 compact stone quite easily broken; two basins of water; six glass tubes absut %" in diameter and 6" lone; 

 twelve narrow strips of blotting paper; three Argand chimneys; three small pieces of cheesecloth and cord; 

 bottle of olive oil; bottle of alcohol; four thermometers; two cups; twelve wide-mouth bottles with corks to 

 fit; 9 little air-slacked lime and powdered charcoal; two pie tins. 



Part A. Composition of Ordinary Field Soils. 



1. By use of a compound microscope, examine a sample of coarse sand; silt loam; clay; 

 muck. Observe the particles of which the various kinds of soil are composed as to — (a) kind 

 of material; (b) average size, i. e., relative to the average size of particles present in other 

 soil samples; (c) average shape of particles; (d) average color. 



2. Place a small amount of air-dry soil in a test tube (just enough to fill the rounded 

 part). Heat gently, (a) Observe any moisture which collects within the tube a little 

 above the soil, (b) Infer concerning the source of this moisture, (c) Most soil, though it 

 appears to be dry will be found to contain what? 



3. Place some clods of ordinary soil in a test tube. Add from one to two inches of 

 water, (a) Observe any bubbles rising to the surface, (b) Soil not filled with water con- 

 tains what? 



4. Observe the samples of soil closely in order to determine whether or not decaying 

 organic matter is present. In which of the four samples do you find the most evidence of 

 such matter? 



5. Put some fresh, moist, rich surface soil into a bottle. Cork it up tightly so as to 

 keep it moist. Write the date on the bottle and then leave it in some light place where 

 you can observe it from time to time. The longer the soil is left, the better, (a) Observe 

 any growth that appears on the surface of the soil. Notice its form and color, (b) Recall 

 having seen moulds and similar plants appear on soils where you had thought no such 

 forms of life were present. From such observations, what may be inferred concerning the 

 presence of small living organisms in soils? 



6. Name five things which you would expect to enter into the composition of ordinary 

 field soils. 



Part B. Some Physical Properties of Soils. 



7. Place a small amount of sand in an evaporating ' dish. Add just enough water to 

 moisten well. Prepare some silt and then some clay in the same manner, (a) Compare the 

 tenacity of sand with that of silt. The tenacity of soils may be roughly measured by the 

 tendency of the wet soil to stick to the fingers, (b) Compare the tenacity of silt with 

 that of clay. 



Another method of ascertaining tenacity in soils is to roll a ball of moist soil in the 

 palm of the hand. Then dry it thoroughly and notice its hardness. 



,R. While stirring a body of wet silt, add wet sand a little at a time, (a) -Observe 

 the effect upon the tenacity of the silt as more and more sand is added. Repeat the ex- 



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