Petrology of Victorian Granites. 215 



tions of monoclinic and triclinic felspars present until a point is 

 reached in which the triclinic felspar is clearly the dominant one. 



To this extreme type there is no difficulty in assigning the term 

 granitite. Between these limits, however, lies a large range of 

 rocks in which the I'elative proportions of the felspars may vary 

 greatly, and it is to be desired that a name existed to apply to 

 these intermediate rocks. The name which might well liave been 

 applied to them is granitel ; this term, however, has been secured 

 for rocks of the aplite type in which mica is either absent or 

 present only in small quantities. The term " granitel " has not 

 as yet received any general adoption, and it is worth considering 

 whether the original signification of the word might not be 

 changed, and the term in future be applied to rocks of granitic 

 type in which neither felspar can be said to predominate over 

 the other. In the present paper, however, I have not adopted 

 this term, and have preferred to classify the rocks in question on 

 the old well-established description of a true granite. So long as 

 the rock is one in which the monoclinic felspar is clearly the 

 important one the rock is a granite, but when the triclinic felspar 

 ceases to be subsidiary to the monoclinic felspar I have adopted 

 the term granitite. In other words, I suggest the extension of 

 the word "granitite" to include all holocrystalline quartz — 

 biotite — rocks in which a monoclinic felspar is not the dominant 

 one, thus bridging over the gap between the granites and the 

 rocks formerly styled granitites. To conclude the question of 

 nomenclature, a normal granite with muscovite added is, adopting 

 the French term, a granulite ; a normal granite with hornblende 

 is a syenite, granitite with hornblende is a diorite, while the 

 somewhat rare case of a granitite with muscovite is called a mus- 

 covite-granitite. 



Examination in the field shows that in a small area rocks of 

 granitic type may vary greatly in macroscopic appearance even 

 when no contact or regional metamorphism may have taken 

 place, and it may therefore happen that to describe fully the 

 granite of a particular district it would be necessary to prepare a 

 large number of slides. This course the author has not been able 

 always to adopt, owing often to the impossibility, in the absence 

 of recently-worked quarries, of obtaining specimens suitable for 

 slicing. Even fresh-quarried granites often are so brittle that a 



