392 CHESTER K. WENTWORTH 



that it is true that microscopic study precedes the final naming of 

 an igneous rock. However, as in the case of igneous rocks, field 

 names based on simple megascopic inspection will be extensively 

 used before detailed studies are made. It is beheved that field 

 names can be more accurately and expressively used if the principles 

 and essential facts of a quantitative classification such as that 

 here proposed are duly recognized. 



