GRADE AND CLASS TERMS FOR CLASTIC SEDIMENTS 383 



of ratio of the geometrical series which seems to the writer to be 

 essential to any thorough quantitative study of the mechanical 

 composition of sediments. 



Using the data shown in Figure i and Table II, the writer 

 has selected the limits conforming to the power series of 2 

 which most closely conform also to the concensus of the opinions 



Fig. I 



of authorities quoted there. The names of the several 

 thus established were then chosen as described above. 



grades 



AGGREGATE TERMS 



The assignment of definite limiting size values to the terms for 

 the aggregates as named below, as well as the rocks named in 

 another part of this paper, will be objected to on the ground that 

 aggregates are not made up in nature of one grade or even of a few 

 grades, and that therefore the names are inapplicable. The author 



