TEXTURAL (iROUPS 



73 



Of these systems, that of the Bureau of Soils has been 

 applied to the largest number of samples and is most 

 widely known. The names which it applies to its dif- 

 ferent groups or separates are as follows: 



1. Fine gravel 2.000-1.000 m.m. 



2. Coarse sand 1.000-0.500 m.m. 



3. Medium sand 0.500-0.250 m.m. 



4. Fine sand '. 0.250-0.100 m.m. 



5. Very fine sand 0.100-0.050 m.m. 



6. Silt 0.050-0.005 m.m. 



7. Clay 0.005-0.000 m.m. 



All that material above two millimeters in diameter 

 is classed as gravel and stone, and in any complete 

 examination must also be taken into account. The 

 material resulting from the above analysis is sometimes 

 termed the fine earth, in distinction from the gravel, 

 etc. That there are distinctions which should be made 

 between the grades of gravel is obvious, for small 



