Grade. 

 Date. . 



(20) 



EXERCISE 4 



Composition of Soils 

 PtJRPOSE. — To determine the composition of soils by the sedimentation 

 method. 



For this work, samples of at least three widely different soil types common 

 in the localitj^ should be examined. 



1. Place about 10 cc. of the soil to be studied in a dry 100 cc. glass graduate. 



2. Fill two-thirds full with water and shake vigorously at intervals for ten 



minutes. Allow to stand until the soil has settled. Then estimate as 

 closely as possible the proportion of the different grades of gravel, sand, 

 silt and clay which are present. 

 Repeat this operation with the other samples. 



Composition of the Soil 



Consult the soil survey bulletin (as directed by the instructor) for the 

 results of a mechanical analysis of these soils. Then plot curves showing 

 graphically their relative texture and the proportionate amount of the 

 different groups of separates. Use the chart on page 78 of "Soils" by 

 Lyon and Fippin as a guide. 



QUESTIONS 



What is a mechanical analysis of a soil? 

 How does it differ from a chemical analysis? 



How do the mechanical analyses of soils made by the U. S. Department 

 of Agriculture differ from the results of above exercise? 



♦Adapted from "Laboratory Manual for Soil Physics" — Mosier. 



