Faulting at Ballarat East. 349 



will be seen that the vertical movement alone would give an 

 apparent lateral displacement OW, whereas the observed lateral 

 displacement is almost always in the opposite direction. [For 

 clearness in the figure, OA is much larger, compared with AQ, 

 than in most actual cases at Ballarat East]. 



The construction in Fig. 3 : Ascertain Q by the observed 

 heaves of two non-parallel lodes (lode and beds, etc.). Od, OD 

 represent their directions of strike, not necessarily actual position. 

 Or, OR their observed amounts of displacement along the fault. 

 Rj, RJ the lines of intersection with- fault of their parts beyond 

 the fault. If these meet at Q, the true direction of movement is 

 shown on plan as OQ, and may, if desired, be resolved into two 

 components as before. 



From Fig. 4, which represents a case where there has 

 been rotation, it will be seen that two points, O, I, are not 

 displaced, either to the same amount or in the .same direction. 

 The determination of a rate of variation of both components of 

 the movement may be made by sufficient observations, and it is 

 evident that either or both components may at some point 

 vanish, and will do so if other conditions remain the same for a 

 sufficient distance. 



The same constructions may be used when the motion on the 

 fault is known in direction or amount, or both, to ascertain the 

 direction and distance at which the lode may be recovered on the 

 same level as the point at which it was lost. 



Zimmerman's rule depends on a construction of this kind. Tf 

 the line of intersection 01 and a perpendicular ON to fault-line 

 be both drawn forward into the unknown ground, the lode is to 

 be sought on that side of the line of intersection on which this 

 perpendicular falls. This is illustrated in Fig. 1, where it gives 

 the correct direction, and in Fig. 2, where it would give the 

 wrong direction. 



Fig. 3 also at once shows that, if the lateral displacement of 

 the lode OD is observed as OR, and it is desired to ascertain 

 that of Od, it is not immaterial to which point on RJ we suppose 

 the point from O to have moved. 



Zimmerman's rule is, in fact, dependent on the following 

 assumpticms : — 



