EXPLANATION OF PLATES 



659 



Plate 45. — Types of Sand Grains 



FiGUEE 1. — ^olo-aqueous SuMype of Sand; Dune, Lale Michigan Shore, Mus- 

 kegon, Michigan. (X20%.) 



Rather flue, well assorted, quartz predominant ; wind action in- 

 dicated by tendency toward the subspherical, away from the sub- 

 angular outline. Collected by Prof. M. S. W. Jefferson. Reflected 

 light. 



Figure 2. — ^olo-aqueous Subtype of Sand; Dune, Pacific Coast, near San 

 Francisco, California. (X20i4.) 



Closely related to figure 1 ; approaching the seolian type ; indi- 

 cated by well rounded outlines. Supplied by the U. S. Geological 

 Survey. Reflected light. 



Figure 3. — ^olo-residual Subtype of Sand, from near Cairo, Egypt. (X 201/2-) 



Poorly assorted as to size ; quartz predominant. The coarser 

 granules are smoothed and rounded, three having been reduced to 

 almost perfect spheres. The finer material has been less affected 

 and remains subangular to angular. Collected by Prof. B. L. 

 D'Ooge. Reflected light. 



Figure 4. — ^olo-residual Subtype of Sand, from Gizeh, Egypt. (X 20%.) 



Well assorted; quartz predominant. Granules subangular to 

 subspherical, with frosted and pitted surfaces. Collected by Mrs. 

 Julia A. Sherman. Reflected light. 



Figures 5 and 6. — Desert Sand from near Albuquerque, New Mexico. 



Showing general similarity with figure 4. If derived by wind 

 action on a residual sand the subtype is aeolo-residual. It is not 

 improbable that some is also seolo-aqueous. Collected by Dr. 

 A. C. Lane. Reflected light. 



