president's address — SECTION c. 133 



trace lias yet been found. With a possible exception — alluded to 

 later on — it is important to note that this ancient metamorphosed 

 sedimentary series, so abundantly represented in Western Australia, 

 have yielded no fossils as yet. 



If, perhaps, I dwell at a somewhat great length upon these older 

 rocks, it is that their economic importance has necessitated the atten- 

 tion of the geological survey being, up to the present, principally 

 devoted to their investigation, rather than to that of the strata lying 

 unconformably above them. 



Time will hardly admit, though there is the inclination, of trespassing 

 upon your time by affecting comparisons with the geology of similar areas 

 of Pre-Cambrian rocks in other countries, nor discussing many of those 

 theoretical questions arising out of the data which have been amassed. 



These older rocks have been studied in more or less detail at 

 different localities throughout the State, distributed over 14° of lati- 

 tude. They consist of rocks of very different types; many of them 

 are in a crystalline condition, and form coarse crystalline schists and 

 gneiss, which differ but little from granite and other rocks of like 

 origin, as well as basic rocks, which have been more or less crushed, 

 foliated, and completely converted into greenstone schists. 



A very important feature of these basic schists is the presence 

 among them of unfoliated rocks, which sometimes occur in the form 

 of lenticular belts of considerable extent — diabase, dolerite, diorite, 

 epidiorite, pyroxenite, porphyrite, ampbibolite, &c. 



In some localities these basic rocks can be seen passing by scarcely 

 perceptible gradations into hornblende schists, while in others are 

 bands of magnetite schist, in the centre of some of which are large 

 phacoidal-shaped masses of greenstone occurring in such a way as to 

 indicate that the margins only of the masses have been ground down 

 into schists. 



Some of these older rocks are of sedimentary origin, and are practi- 

 cally unaltered ; others are quartz, mica schists, and granulites. Whilst 

 these represent the two extremes, there are intermediate forms which 

 link them together. The less altered members of these older rocks 

 make their appearance in many portions of the State. The rocks con- 

 sist of a great variety of types of indurated slates, quartzites, and 

 conglomerates, together with igneous rocks, some of which there are 

 very good grounds for believing to have been originally lavas and ashes. 



Many of these old crystalline rocks have been so altered as to 

 possess characters which cannot be looked upon as original, because 

 many of them have lost not only their individuality but also their 

 geological identity. 



A remarkable and very noticeable feature of these older rocks in 

 most localities in which they have been examined are those bands of 

 laminated quartzites and jaspers (which often contain oxide of iron 

 to such an extent as to warrant their being classed as iron ores). These 

 extend as roughly parallel bands, sometimes several miles in length, 

 in the form of attenuated lenses, which, owing to their serrated ridges, 

 stand out in bold relief, thus acquiring a conspicuousness perhaps 



