124 Transactions of the Royal Society of Victoria. 



crystallised. For the present I must leave this in a state 

 of doubt. 



At this point the diagram section terminates, but the 

 granites extend westwards, without break, along the course 

 of Wilson's Creek, to its junction with Livingstone Creek, 

 and thence to the hills on the western side. When examin- 

 ing these hills, I found that the granites still extended, 

 with slight alteration of composition, and that in places they 

 assumed a gneissose structure. But I did not, within a 

 distance of about two miles from Livingstone Creek, meet 

 with even any traces of such schists as those which I have 

 described as being on the north-eastern side of the contact. 

 How far to the west the granites extend, I am at present not 

 able to state.* 



The porphyritic structure of the granites of Wilson's Creek 

 is well ma.rked, and on the western side of Livingstone Creek 

 the felspar, which is the porphyritic mineral, is in places 

 remarkably fresh and unaltered. I examined one of these 

 felspars, with the following results : — 



Analysis No. 10.- 



-Orthoclase 



^Micropertl 



Si.O, 





63-60 



ALA '- 





20-20 



Ca.O 





•31 



Mg.O 





•15 



K^O 





8-05 



Na-aO 





6-43 



H^O 





-52 





99-26 



In this felspar the optic axial plane is perpendicular to the 

 plane of symmetry, with horizontal dispersion, as is usual in 

 orthoclase. 



In a thin slice prepared from a basal cleavage plate, the 

 main field obscures parallel to the edge P.M., but there are 

 places which obscure at an angle of about 3° from that 

 direction. Small interpositions of quartz and of a second 

 felspar are in veinlets, and also in the direction of the prism, 

 00 P. (-110). The felspar veinlets are probably albite, and 

 do not differ from analogous interpositions in some of the 



* This examination does not refer to the country south of the junction of 

 Day' s Creek with Livingstone Creek. 



