206 Rev. 0. Fisher — On Faulting, Jointing, and Cleavage. 



FlQ 



The relative throw of A and B, however, might be called equally 

 well 6 — a. The choice between the two expressions depends upon 

 whether any given point in A got the greater throw downwards at 

 the first or at the second movement. 



(5.) To obtain these results at once by 

 trial lines, suppose a a,bb, to be the outcrops 

 of two faults, the arrows showing the direc- 

 tions of their hades. 



Then it is evident that a hades under X 

 and B, but not under A ; while h hades under 

 X and A but not under B. Hence a trial 

 line put down in — 



A indicates a throw b. 

 B ,, ,, a. 



X ,, ,, a -\- b. 



We further see that one put down in Z 



will cut neither fault. Hence Z is not 



thrown, and must therefore be continuous with the hidden mass Y 



below, as upon consideration it will be seen to be. 



The relative throw of any two masses will be the dififerencQ 

 of their total throws ; so that the relative throw of — 

 A and £ is a — ,b ; 

 A „ X ,, a; 

 B „ X „ b. 



It might happen that the throws of the first and second faults 

 were equal, or a = h ; and then the throw of A with respect to B 

 would be nothing, that is the beds of A and B would be left on a 

 level with each other. The beds of X however would be depressed 

 through a with respect to either A or B. In such a case, the 

 throws of A and B being the same with respect to Y (see Fig. 3), 

 the two faults would cross one another at the apex of the wedge 

 X, and a trial line passing through the apex would miss a thickness 

 2a of beds all at once. 



This method is easily ex- 

 tended to any number of faults. 

 Suppose the figure to represent 

 the outcrops of a system of 

 faults, hading in the directions 

 indicated by the arrows, and 

 having throws a, h, c, d, e, re- 

 spectively, and having occurred 

 in that order in time. Then 

 to take four instances only, we 

 have merely to notice which 

 faults a trial line would cut. 

 Thus— 



The total throw of P 



„ >> s 



The relative throw of P and Q 



„ „ of Q auiE 



will be 



c -\- d -{- e, 



a -\- e, 



a -\- d -{- e, 



ff-f *. 



c -\- d — a; 



and so on. 



