Art. II. — FurtJter Notes on the Igneous Rocks of South 

 Western Victoria. 



By J. DENNANT, F.G.S., F.C.S. 



[Read 13th June, 1901.1 

 (With Plate 1.). 



In the present paper I propose to supply a few additional 

 details concerning some of the volcanic I'ocks described in a 

 general manner a few years ago.^ 



Before doing so I wish to clear away a misapprehension which 

 has arisen owing to the scheme of shading adopted in the map 

 accompanying my former article. Both the olivine basalts and 

 the typical sanidine-bearing series of rocks are there similarly 

 shaded, not because I regarded them as identical, but simply 

 because my researches were too imcomplete to enable me to 

 define with even approximate accuracy their respectiv^e boundaries. 

 As a fact, these two classes of rocks are so intimately associated 

 in certain portions of the area that their separation can only be 

 attempted on maps drawn to a large scale. 



Since I drew attention to these rocks in 1893, the geology of 

 the district has been reported upon by Mr. Ferguson, of the 

 Geological Survey, who discovered a glacial deposit in the 

 neighbourhood of Coleraine. Still later, Mr. E. G. Hogg has 

 given a fuller account of the same deposit, and has besides 

 examined the sanidine-bearing rocks with the result that he 

 classes them as trachytes. 



The first rock referred to by him occurs at Mounts Adam 

 and Eve, and is described as light colored and porphyritic. It 

 is of course a highly altered rock, and I gather from Mr. Hogg's 

 subsequent remarks that his real type of the trachyte is the 

 green, fresh-looking rock close at hand. Unaltered examples of 

 such rocks are as a rule found only in the deeper quarries, since 

 they weather readily and to a considerable depth from the 



1 Aust. Assoc. Adv. Sci., Adelaide, 1893. 



