MANUAL OF GENERAL AGRICULTURE. 7 



PART I. PHYSICAL PROPERTIES OF SOILS. 



1. HOW SOILS ARE FORMED. (FIELD EXERCISE.) 



(a) Work of Atmosphere. 1. Note any rocks worn 

 away by the friction of wind or sand through the action 

 of the wind. Note any rocks kept exposed to other at- 

 mospheric agencies through the action of the wind; note 

 any wind-blown soil; any wind-blown water. 



2. Note any evidences of chemical action; oxida- 

 tion; action of carbon dioxid; ''rotten rock." Make a 

 drawing showing successive stages of disintegration from 

 solid rock to soil. 



(b) Work of Water. 1. Note any evidences of its 

 solvent power. Fill a small bottle with clear water from 

 a spring or brook and when you return to the laboratory 

 evaporate a few drops of it on a piece of glass or in a test 

 tube, and see if there is any residue ; explain. 



2. Disintegrating Power of Water. Note evidences 

 of the washing out of loose material, and of cutting 

 power of the water; of the abrasion caused by gravel, 

 pebbles and stones. 



3. Transporting Power of Water. Why is one 

 stream clear, and another muddy? Note any sand or 

 soil dropped by water. 



4. Note evidences of assorting power of water. 

 Draw a section of the bank of a stream, showing stratifi- 

 cation. 



5. Note evidences of under-ground streams, of land- 

 slides, and describe and explain. 



2. TAKING SOIL SAMPLES. (FIELD EXERCISE.) 



Materials: Spade, pai$ two one quart fruit jars, 

 or two bottles with corks. 



Select a spot for sampling and remove any leaves 

 and twigs from the surface. Dig into the cleared space 

 a V-shaped hole, with one side of the V perpendicular. 

 On the perpendicular side measure the depth to the 

 change in color, which indicates the division between sur- 

 face soil and subsoil. With the spade shave thin slices 

 from the perpendicular side to the depth of the surface 



