AGRICULTURAL NATURE STUDY OUTLINES 
35 
Rocks .—How formed? Explain granite, lava, slate, sandstone, 
limestone. Have specimens in the schoolroom for a discussion on the 
origin of soil. Relation of rocks to the earth’s crust. What is sedi¬ 
mentary rock? Look at small stones along the edge of a stream or in 
the dry bed. What are the various shapes? What has caused the 
changes ? What are the fossils sometimes found in rocks ? What forces 
cause the decay of rocks? What are some of the common minerals 
found in rocks ? 
Air .—Different elements that compose the air How deep or thick 
is the layer of air surrounding the earth? How heavy is the air or 
what is its pressure? Why do we not feel this pressure? What do 
we mean by the temperature of the atmosphere ? How do we measure 
it? Why does the air get colder as we go up? What causes winds? 
Necessity of air for animals and plants. Air in soil and water. How 
is air made impure? Explain how carbon dioxide is made. What 
relation does oxygen have to combustion ? How is nitrogen valuable 
to plant life ? If the atmosphere at sea level weighs fifteen pounds to 
the square inch, and if four-fifths of this weight is nitrogen, how many 
pounds of nitrogen are pressing down on every acre of the earth’s 
surface ? 
VI. OUTLINES FOR THE SIXTH GRADE 
1. Human Needs, Interests, and x\ctivities 
Silo construction .—Number of silos in the community. Any in the 
process of construction? Children get data as to materials used, 
wood, concrete, brick, stone, or steel. Method of construction. Size 
and shape of a silo. Children estimate the volume of a silo in pounds. 
Find out how many pounds of silage are fed daily to a cow. Estimate 
how long the silage in this particular silo would last for a herd of 
ten cows. Advantages of a silo. See Circular 138 of the College of 
Agriculture at Berkeley on “The Silo in California Agriculture,” 
bv F. W. Woll. 
Correspondence courses in agriculture .—Through the pupils of 
the school make an agricultural education survey of the district to 
ascertain how many are enrolled in the correspondence courses of the 
Division of Agricultural Education of the University of California. 
Send for Circular 113, which describes the character of these courses. 
Many of these courses will prove of value to the teacher in the work 
of the seventh and the eighth grades. 
