STRUCTURAL RESULTS OF FAULTING. 165 



contact W P^. This energy will be distributed through the system, and 



were the friction uniform the resulting curve would be a simple logarithmic 



one. But as the friction will decrease towards the surface, the locus will 



be approximately 



A m~'^ 



To produce this configuration, however, an energy of only 



is required, and the system will consequently reach it with a vis viva 



The system will continue its movement till this energy is expended and its 

 final configuration will be 



y = {A + A,) 



[—xt' 



Experimental verification. — If the various assuniptious made are correct, a 

 fault under certain conditions will result in a surface, a vertical section of 

 which at right angles to the strike of the fault will present a logarithmic 

 curve. Before proceeding to any further deductions, it is evidently desir- 

 able to test the correctness of the postulates experimentally. I have sup- 

 posed the sheets of rock of infinite size as compared with their exposed 

 margins, because on this supposition the pressure per unit of area of each 

 parting will be the same. If the plates were thoroughly flexible, and if 

 the pressure were applied on a limited zone parallel to the croppings and 

 removed by a distance greater than b from either end of the plates, then 

 the pressure exerted on each plate would be the same, and would be dis- 

 tributed over an equal area, and the resulting curve would still answer to 

 the general formula deduced. These conditions we can approximately 

 reproduce. If a pile of, say, one hundred slips of very thin, flexible and 

 uniform paper, eight or ten inches long, with sharply cut edges, are laid 

 upon a flat surface, and a narrow weight of three or four pounds is placed 

 across them, the pressure imder the weight may be considered as constant. 



