488 



GEOLOGY. 



The bedding of conglomerate is due chiefly to variations in coarseness. 

 Laminae or thicker layers of sand are frequently found between layers 

 of coarser material. Conglomerate is likely to be thick-bedded, and 

 cross-bedding is common. 



Lateral gradation. — When the varying nature of the agitation of the 

 sea at different depths and along the different parts of the coast-border, 

 and during different phases of the sea-currents, is considered, it will be 

 readily understood that sedimentary beds are affected by many irregu- 





^^:^ 



Fig. 368. — Cross-bedding in sandstone. Dells of the Wisconsin near Kilbourn, Wis. 



(Bennett.) 



larities, and that deposits of one kind grade into others horizontally 

 with great freedom. Thus a bed of conglomerate (gravel) may grade 



