chloric acid. The action of the acid upon this rock is like its action upon what mineral? 

 What then appears to be the essential mineral present in limestone? (e) Observe any resi- 

 due left in the bottom of the tube after the mineral which forms the bulk of the limestone has 

 been dissolved. Infer the kind of soil which would result from the dissolving of limestones. 



5. Extensive beds of mud made up of silt and clay are being deposited in large bodies of 

 water. Under moderate heat and pressure these beds may at some later era become shale. 

 Under great heat and pressure they may even become slate, (a) From your study of the 

 durability of minerals, infer what class (weak or durable minerals) forms the bulk of shales, 

 (b) State the colors of the shale specimens at hand, (c) Describe their feeling when wet. 

 (d) Hardness? (e) Solubility? (f) Porosity? (g) Compare the durability of shales with 

 the durability of other rocks studied in this lesson, (h) Infer the nature of soil resulting from 

 the weathering of shale. 



6. (a) In general, what kind of minerals, as regards durability, tend to form sand? (b) 

 What kind of minerals tend to form silt or clay? (c) How do you explain that the weather- 

 ing of granitic rocks often gives rise to a soil containing a large per cent of gravel and sand? 

 (d) Limestones often give rise to large areas of silt and clay soils. Explain. 



Part B. Transportation and Sorting of Soils. 



7. Although most soils are derived from disintegrated rock, the belief that soils are de- 

 rived from the rock which lies just beneath them is oftentimes faulty. Disintegrated material 

 from any locality, or from any one kind of rock, may have been carried from the place of 

 formation and mixed with materials from various rocks of other localities. Thus mixed, this 

 material may be deposited in still another place with or without being sorted according to 

 size and weight of particles. It is roughly estimated that at least 90 per cent of the soils of 

 the United States owe their present position and distribution to the action of moving water, 

 moving ice, and moving air. 



What kind of soils contain relatively little disintegrated rock material? Reference: 

 "Soils," Lyon and Pippin, page 41. 



8. Thoroughly mix some dry, coarse sand with some dry, pulverized silt loam. Fill a 

 test tube about VA" deep with the mixture. Now fill the test tube about full of water. Shake 

 the tube until the soil and water are well mixed. Allow the soil to settle. What change has 

 taken place in the arrangement of the various sized particles? 



9. Place a handful of sand in a shallow basin of water. Whirl the water in the basin, 

 (a) Allow the water to come to rest and observe whether or not there has been any ten- 

 dency to sort the sand according to the size of particles, (b) In what part of the basin did 

 the water acquire the greatest velocity? (c) Are large or small particles deposited in that 

 part of the basin? 



10. Place a small pile of the mixed sand and silt on a sheet of note paper. Blow gently 

 through a glass tube against one side of the pile. What change takes place in the arrangement 

 of the various sized soil particles? 



11. Move your hand horizontally against a small amount of mixed silt and sand spread 

 out on a flat surface. If a solid, such as ice, caused the pile to move, would there be any 

 marked tendency to sort the particles according to size? 



12. Figures 1, 2 and 3 illustrate some typical soils, (a) What evidence is there that 

 Figure 1 is taken from a photograph of water-laid soils? (b) Figure 2 shows what evidence 

 of an ice-laid soil? (c) Figure 3 shows what evidence of being wind-laid? 



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