346 Frocaedings of the Royal Society of Victoria. 



It is noticed by ]\Ir. Lidgey, that the north-easterly crosscourses 

 of this field are most numerous and appear most important, several 

 of them have larger displacements than any known north-westerly 

 crosscourse. On the north-easterly crosscourses, the hanging wall 

 side has generally a relative movement downward and forward 

 in a south-westerly direction. This is the general direction of dip 

 of most of the slides. The crosscourses are, however, newer 

 than the slides and displace them, l)ut the existence of the 

 slides may have facilitated the movement in this direction, 

 and contemporaneous further movement on the slides might 

 easily produce an abrupt change in the displacement on the 

 crosscourses. 



TAg oiAer fauUs. ^The slides are in all cases reversed faults, 

 and the strata are usually much bent near them. If we regard 

 the strata as vertical and the movement as along the line of dip 

 of the fault, then the heave due to any throw = throw x 

 co-tangent of angle of inclination of fault to horizontal plane x 

 cosine of angle between strikes of fault and strata. As the 

 angle of inclination of the fault is usually about 45", and the 

 angle between the strikes usually less than 10°, both these ratios 

 are nearly unity, and we would expect to find throw and heave 

 about equal, as they are by observation. But it does not appear 

 how the throw has been ascertained; if it is simply the difference 

 of level of the two points in a vertical plane at which the 

 indicator (or any other bed) meets the fault from the upper and 

 lower sides, then it must necessarily agree with the apparent 

 heave of the same bed, for (as is shown later by Fig. 1), the 

 two quantities are not independent. Similar remarks apply to 

 other strike-faults of which the direction and dip are different. 

 The observed facts are in any case not inconsistent with a typical 

 reversed fault, and the striations, in some cases at least, support 

 the view that the motion has been in the direction of the line of 

 dip of the fault. 



There does not appear to be any very real difference between 

 these slides and those which occurred prior to the formation of 

 the quartz reefs, some of which are themselves occupied by quartz 

 reefs. The periods of formation of the strike faults and of the 

 quartz veins and lodes appear to have overlapped. 



