FIG. 21. Sand Grains 

 (magnified). 



(From a Photograph kindly lent 

 by Dr. C. G. CULLIS.) 



FIG. 20. Ripple Marks and Footprints, Triassic Sandstone. 

 Storeton. 



(Photo by GODFREY BINGLEY.) 



FlG. 22. Boulder Clay, near Richmond, Yorkshire. 



(Photo by GODFREY BINGI.EY.) 



