XVlll 



gonite (hydrous silicate of iron, etc.), obtained near Perth. 11. 

 Pyroclore"(columbato and lilanate of calcium). This rare mineral, or 

 a species closely allied thereto, has been discovered on the property of 

 the Shakelton mining syndicate near Table Cape. It occurs in a 

 granular condition of a brown colour in alluvial drift with zircon, 

 sapphire, and quartz. 12. Prosopite (hydrous, fluoride of aluminium, 

 and calcium), abundant as a white, powdery substance at the " White 

 Faces," Mount Bischoff. 13. Pyrrnotite (sulphide of iron) occura in 

 enormous quantities, Colebrook mine, N.E. Dundas, with arsenopyrite 

 and chalcopyrite intermixed. 14. Sillimanite (a basic ortho-silicate of 

 aluminium), recently discovered by Mr. W. F. Twelvetrees and the 

 writer as occurring as sillimanite-schist at the Lucy River, a tributary 

 of the Pieman, and at Mount Stuart, Heazlewood district. 15. 

 Tetrahedrite (sulphantimonite of copper) occurs disseminated through 

 the ore of the Tasmania G.M. Co., lieaconsfield, and at the Hercules 

 miue, Mount Read, where some remarkably fine bunches occur. 16. 

 Uralite (a pseudomorphous hornblende with the external form of 

 augite). 17. Vanadinite (an orthovanadate of lead with chloride of 

 lead), silver mine near Waratah. 18. Zinkenite (sulphantimonite of 

 lead). At Block 291, North-East Dundas, some beautifully developed 

 crystals of this mineral are obtained. They occur attached to siderite, 

 with pyrite, tetrahedrite, and more lately crystals of argenite. 19. 

 Zinnwaldite (lettia muscovile) occurs in granite, and thus forms the 

 common white mica of the stanniferous rocks of the East Coast. 



SPHERULITIC FELSITE ON THE WEST COAST. 



A papar by Mr. W. H. Twelvetrees, F.G.S., and Mr. W. F. Petterd, 

 C.M.Z.S. was read, showing that examples of this rock from four different 

 localities had come under their notice, namely, from Zeehan, the 

 Castray River, Trial Harbour, and Strahan, and they described the 

 character of each. 



Mr. R, M. Johnston spoke in eulogistic terms of the valuable 

 contributions to the literature and scientific information possessed 

 by the society by Mr. Petterd and Mr, Twelvetrees. He would also 

 compliment the proprietors of The Mercury upon the admirably 

 executed illustrations prepared in connection with these gentlemen's 

 papers. 



THE GREAT LAKE AND ITS WATER POWER. 



Mr. A. Mault read a paper on this subject. He said it was the 

 largeet and highest above sea level of the more important lakes of 

 Tasmania. It is situated on the great central plateau of the island, 

 about 93 miles by rail and road north-west of Hobart. Its watershed 

 basis has an area of 225 square miles, of which 44 square miles are 

 occupied by the lake itself. " Walch's Red Book " mentions it as 

 being 3,700ft. above sea level, but he calculated it at 3,281ft. The 

 lake is said to be very shallow for its great size, as not more than 

 between 30ft. to 40ft. in depth has been found. The water is more 

 discoloured and turbid than it used to be, said to be due to the 

 ochreous clay that results from the disintegration of the igneous rocks 

 of the country. The writer then spoke of the enormous water-power 

 the lake might afford, and how the supply could be regulated so as to 

 ensure a constant and continual sufficiency. The River Shannon was 

 the only outlet of the waters, being about 30 yds. wide at the outlet, 

 where a rocky bottom prevents the lowering of the surface of the 

 lake more than about 4ft. below high- water level. The Shannon has a 

 meandering course of about 36 miles, through hilly country to the River 



