INAUGURAL ADDRESS. 4& 



Leichharclt in the drainage area of the River Roper may indicate 

 a Cretaceous formation rather than a Palaeozoic one ; Leichhardt 

 reported finding " impressions of bivalves, one ribbed like a 

 Cardiumr whilst Jukes, without sufficient warranty, conjectured 

 they may have been Sp'iriferce or Product ce, and colored the area as 

 probably Palseozoic. That two, if not three, geological epochs are 

 represented by similar lithological and physiographic developments 

 is not at all improbable ; and the origin of the tableland sandstone 

 may be sought in the denudation of the Carboniferous quartzites 

 of the western coastal region, whilst the reconstruction of the 

 tableland sandstone may have originated some of the minor 

 sandstone formations on the north coast, as suggested by Wilson. 



MICROSCOPIC PETROLOGY. 



Geologists have been too busily engaged in reaping golden 

 harvests in the domains of pala;ontology and stratigraphy to be 

 much tempted by the allurements of chemical geology or micro- 

 scopic petrology. 



Professor Ulrich has on several occasions drawn attention to 

 the desirability of the microscopic study of our rocks as an aid to 

 the explanation of geological phenomena, especially because useful 

 generalisations could be drawn from the characteristics of certain 

 intrusive rocks. Mr. A. W. Howitt has been zealous in his 

 researches in this direction, and has been of late ably supported 

 by Mr. W. Anderson, Rev. Milne Curran, Professor David, and 

 Mr. James Stirling. This modern method of petrographical 

 research, when employed .as an aid to stratigraphical investigation,. 

 promises to be a source of important discoveries in Australian 

 geology, pai'ticularly in that portion of it relating to the history 

 of our volcanic rocks. 



SUMMARY OF DISCOVERIES AND ORIGINAL 

 RESEARCHES. 

 FUNDAMENTAL ROCKS, OK ARCHAEAN. 

 The generalisation which has sought to sweep all the crystalline 

 rocks of Australia into the great Silurian net has been broken 

 down by the discovery of unconformably superimposed Cambrian 

 strata ; and though it by no means follows that the whole of the 

 crystalline rock masses are of Archsean age, yet there are good 

 reasons for the belief that those rocks which exhibit the phenome- 

 non of regional metamorphism belong to one epoch. The chief 



