112 Transactions of the Royal Society of Victoria. 



and fine-grained beds, with the Jess altered formations in the 

 same sequence in the Bowen Mountains, which can be again 

 followed across their strike still further to the eastward, to 

 where in the Tambo Valley, between Tongeo and Bindi, they 

 have all the familiar facies of the Silurian strata of the 

 district. I regard these schists as being metamorphosed 

 lower palaeozoic sediments, and in all probability of lower 

 Silurian age. 



Under the microscope, I found a thin slice prepared from 

 one of the fine-grained beds, to be a minute mixture of small 

 flakes of a colourless alkali mica, with a very little magnesia 

 mica of a yellowish colour, and a small amount of quartz in 

 oTains of minute size. 



Throughout the whole mass, there is much graphite 

 distributed in minute specks, which in places are aggregated 

 into small masses. Of this rock I made the subjoined 

 quantitative analysis : — 



Analysis No. 



6. — Mica Schist. 



C 







3-32* 



P2O5 







•10 



Si.02 







6400 



A1.A 







19-82 



Fe.A . 







3-50 



Ca.O 







•32 



Mg.O 







214 



K,0 







4-41 



Na.,0 







MO 



H,0 







223 





100-94 



Hygroscopic Moisture ... '85 



Sp.gr. ... ... 2-651 



I also examined a quartzose schist which adjoined the 

 above. I found it to be composed mainly of grains of quartz, 

 some of which contain numerous fluid cavities. Surrounding, 

 and lying between the quartz grains are small ragged flakes 

 of magnesia mica, which are much bleached in colour, and 



* As this percentage of graphite appeared to me to be high, I made a second 

 determination for control, which gave 3-40 per cent. The graphite which 

 separated, on treating the finely powered rock with pure hydrofluoric acid 

 and sulphuric acid, and boiling the residue with water, was apparently in a 

 pure state, but on ignition for nearly two hours left a considerable ash. 



