1 30 Clicvpraan and Thiele : 



dense, hard, blue basalt of volcanic neck No. 3^ may possibly be 

 allied to ours. Those rocks falling into type r of Kitson most 

 nearly approach that from Balvvy n. They are described as "A dense 

 or fully crystalline basalt as a rule, with or without amygdules 

 of calcite and small patches of olivine. This occurs as small 

 plugs and dykes.""- These rocks are regarded by Mr. Kitson as 

 post -Jurassic in age, and almost certainly contemporaneous with 

 the older basalt of Flinders and the Mornington Peninsula. 



An interesting occurrence of some small plugs of dense black 

 prismatic basalt, from south of Woodend, Macedon district, has 

 been lately described by Professor Skeats,'' who refers them to 

 the limburgites. In section this rock " shows phenocrysts of 

 fresh olivines, set in a dark, dense, tine-grained ground-mass, 

 consisting of lath-shaped minute augites, magnetite and small 

 felspars with a residuum of dark glass." The age of this rock 

 Professor Skeats provisionally regards as middle cainozoic (?). 

 In noting the structural likeness of the Woodend limhurgite to 

 that from Balwyn, it strikes one as very probable that similar 

 volcanic effusions may yet be found traversing the older rocks 

 in the area between the last-named locality and the district of 

 Central Victoria, especially since the Balwyn occurrence seems 

 to be a plug which has been uncovered by denudation from the 

 action of the present river system;^ and thereby indicating the 

 possible proximity of other effusions which have not quit© 

 reached the upper limiting surface of the basal rocks, or have 

 shrunk down again within the pipes they may have formed. 



Turning to New South "Wales, in the neighbourhood of 

 Sydney, notably near Parramatta, there are numerous plugs of 

 basic lavas ranging through the limburgites, magma basalts and 

 augitites. These rocks are often indicated on the surface as a 

 series of isolated lenses, and they frequently end abruptly at a 

 few feet from the present land surface ; whilst the shales 

 through which they rise appear shattered.^ The Sydney basic 



1 Ibid, lot-, cit., p. 156. 



2 Loc. fit., p. 156. 



'6 Pres. Address, Sect. C, Austr. Asisoc. Adv. Sci. (1009), p. -im. 



4 It is within the recollectioii of one of us (A.O.T.) that the early excavations were 

 made in two or more places, and those undertaking- it were guided by the stones lying 

 on the surface. 



5 M. Morrison — " Notes on some of the Dykes and \'olcanic .Necksof tlie Sydney District, 

 €tc." Records (ieol. Surv., N. S. Wales, vol. vii., pt. iv. (1004), p. -262. 



