president's address — SECTION c. 13^ 



kidney or damper-shaped lenses of quartz, whicli vary from a few inclies 

 to a foot or so in width. The interval between each lens of quartz 

 fluctuates within very wide limits. 



The walls of the country enclosing these lenses are scored with 

 strise in the direction of the movement in a vertical direction, and the 

 faces of the striations are often coated with fine films of gold. The 

 abnormal richness — nearly 3ozs. per ton — of this type of auriferous 

 reef has resulted in its being extensively prospected almost along the 

 whole length, hence abundant opportunities are afforded for investigating 

 its peculiarities both on the surface and below ground. 



The ancient sedimentary beds of Warrawoona, which are highly 

 siliceous rocks, dipping at varying angles to the north and east, consist 

 of fine-grained flaggy quartzites, conglomerates, and quartz schists. 

 Some of the conglomerates still retain traces of their original character, 

 though in others most of the pebbles have been flattened out and 

 stretched almost beyond recognition. 



The oldest series of basic dykes, by which they are traversed, 

 have also been crushed and sheared, and are now represented by bands 

 of schistose greenstones. The rocks are also intersected by certain, 

 other acidic dykes now represented by quartz sericite schists, which 

 may have originally been porphyries. One example from Warra- 

 woona is a quartz sericite schist, with " eyes " of a fairly soft mineral, 

 originally a potash felspar, around which the finer foliation of the matrix 

 sweeps in very graceful curves. When submitted to microscopic 

 examination it is found that these porphyritic crystals present that 

 peculiar peripheral granulation so characteristic of crystals and frag- 

 ments which have been subject to intense crushing. 



All the features, both of the rocks and the reefs, coupled with other 

 evidence, clearly indicate the presence of a number of overthrust and 

 normal faults, and point to a series of movements along lines parallel 

 to that of the main trend of the dominant structural features of the 

 district, which is north-west and south-east. The disruption of the 

 newest series of basic dykes, to which reference has been previously 

 made, indicates that the enormous terrestrial stresses and strains con- 

 tinued in the same locaUty over a wide interval of geological time. 



Traces of life may perhaps have existed in these old rocks of the 

 North-West. Amongst the quartz schists which form the lofty serrated 

 summit of the main axis of Warrawoona is a bed which here and there 

 contains what at first glance appears to be fossil wood. A character- 

 istic specimen of this sihcified wood (?) has a length of about 4iin. ; 

 cross sections of it are ellipsoidal in shape, the major axis being about 

 fin. and the minor axis about fin. in length. 



Microscopical sections, both transverse and longitudinal, were 

 prepared and submitted along with the specimens to Mr. Etheridge, 

 of the Australian Museum, who, however, was unable to detect any 

 trace of organic structure in them. It is, however, quite possible 

 that some form of organic life existed at the time these beds were de- 

 posited, and that the marked changes which they have undergone 

 obliterated all traces of organic structure. 



