PRACTICE XXXII 



STANDARDIZATION OF THE EYEPIECE MICKOMETER 



Use eyepiece and stage micrometers. 



Place both micrometers in position and determine for each of 

 the objectives the number of divisions or spaces of the eyepiece 

 micrometer that corresponds to 1, 0.1, 0.01, and 0.001 milhmeters 

 of the stage micrometer. 



Show on the table below the number of spaces of the eyepiece 

 micrometer that corresponds to the size of the various grades of 

 soil particles. By means of this table and the microscope with 

 the eyepiece micrometer it may be determined whether the 

 separations are properly made in the following practice. 



Grades 



Diameter in 

 Millimeters 



Number 



IN 



OR Inch 



OF Spaces 



Mm. 



Objective 



Number of Spaces 



in Mm. 



on Inch Objective 



Clay 



less than 0.001 







Fine silt 



0.001 to 0.0032 







Medium silt 



0.0032 to 0.01 





Coarse silt 



0.01 to 0.032 



! 



Fine sand . 



0.032 to 0.1 





Medium sand 



0.1 to 0.32 







Coarse sand 



• 0.32 to 1.0 







Fine gravel 



1.0 to 3.2 ' 







Medium gravel ...... 



3.2 to 1.0 







Coarse gravel 



1.0 to 32 





Stones ■• 



32 and larger 





• 



65 



