98 THE PHYSICAL PROPERTIES OF SOILS 



In order to secure a sample that will be representa- 

 tive of a given field or plot it is necessary to drive 

 down a sampling tube in a number of places and com- 

 bine the cores into a composite sample. A moisture 

 determination made in duplicate on this composite 

 sample may be taken to represent the average moisture 

 of the soil over the field under observation. 



Samples taken for mechanical analysis should be 



METHOD OF SUB-SAMPLING SOIL BY SUCCESSIVE DIVISIONS 

 OF THE MAIN SAMPLE 



dried, thoroughly mixed, and the lumps broken with 

 a rolling-pin. They should then be passed through a 

 2 mm. sieve to remove the gravel and sticks. The 

 portion of the sample passing through the sieve is 

 spread out on a piece of heavy paper and thoroughly 

 mixed with a large spatula. The sample is then 

 divided into four parts and one portion is again 

 thoroughly mixed. A twenty or thirty gram sample 

 is taken from this fine material, dried in the oven and 

 used for the analysis. 



The method of taking the sample and its subsequent 

 treatment will vary with the purpose for which the 

 sample is taken. 



