516 



GEOLOGY. 



Fig. 421. Fig. 422. 



Fig. 421. — The fault above grades into a fold below. Thickening and thinning of 

 layers next the fault-plane evident. Based on experimental results of Willis (13th 

 Ann. Rept., U. S. Geol. Surv.) 



Fig. 422. — Fault below grading into fold above. Stretching and thinning, and shorten- 

 ing and thickening of beds under pressure is involved. Based on experimental 

 results of Willis. 



Fig. 423. — Diagram showing a fault grading into a monochne horizontally. 



Fig. 424. — Slitekenside surface. (Prestwich.) 



