928 E. W. SHAW SORTING IN SEDIMENTARY ROCKS 



designated the integral and the cumulative, seem to be most expressive. 

 In the first, the amounts of grains of each size are represented by columns 

 having heights corresponding to the percentages as given in the analysis, 

 the coarsest being represented on the left and the others following in reg- 

 ular order. The second differs in that each column represents the grains 

 of one size plus all of larger size. If each column in the integral diagram 

 represents particles averaging two or a multiple of two times the diameter 

 of the next on the left, the highest column, conveniently designated as 

 the maximum, is likely to be centrally located, and the height of the other 

 columns generally decreases more or less regularly from this central col- 

 umn outward. If the centers of the tops of the columns be joined by 

 straight lines, these lines together have a form resembling more or less 

 closely a curve of probability, and to this curve they obviously have a 

 logical relation. Analyses that give the highest maximum column are, 

 of course, the best sorted. It should be noted that mechanical analyses 

 are not so precise as they appear to be, and great precision is not only 

 impracticable, but perhaps not greatly to be desired. 



Sizes of Grains in Separates 



Mechanical analyses have been made by various men and organizations, 

 and there are almost as many systems of sizing as there were men and 

 organizations. Still, few have used the actual number of particles of 

 various sizes, and no one has put the separation on a purely arithmetical 

 basis. For example, no one has classified the particles making up a sedi- 

 ment, each of which differs from the next size by a millimeter. There 

 seems to be rather general agreement in making the size of grains in 

 each separate about twice the diameter of the next coarser, though, very 

 often a separate is made in which the size of the particle is ten times the 

 size of that of the next smaller. Very few have used a single ratio con- 

 sistently throughout. Udden, one of these exceptions, makes the size of 

 grains in each separate twice the diameter of the next smaller, or, rather, 

 in each separate the particles of maximum size are twice the diameter of 

 those of minimum size. No one seems to have made separates on the 

 basis of cubical content or weight of the individual particles, and no one 

 has used consistently the cross-section areas of the particles. 



Significant Features op Diagrams 



If a few hundred analyses of sediments of various origins selected at 

 random, or, better, with the idea of using the most representative ones. 



