ABSTRACT OF PROCEEDINGS, MAY, 1903, 



The monthly evening meeting of the 

 Royal Society of Tasmania Avas held in the 

 evening of the 12th Maj;, 1903. The presi- 

 dent. His Excellency Sir Arthur E. Have- 

 IocIl, G. C.S.I. , presided. 



Apologies. 

 The following telegram from Senator 

 Maofarlane was read: — "Launceston. 

 Kindly express to your meeting ito-night 

 my regret engagement here prevents my 

 presence to hear and discuss such import- 

 ant paper as Tasmania's manufacturing 

 developments." Sir Eliot-t Lewis and 

 Mr. E. C. Patterson also sent apologies. 



Election of New Fellows. 

 The following new members were elect- 

 ed Fellowis of the Society: The Eight Rev. 

 Dr. Delanv (Bishop of Laranda), Drs. A. 

 J. J. Triado and E. J. Roberts, and Mr. 

 A. G. K. Money. 



Royal Medals. 



The President read a letter fro-m Lord 

 Francis Knollys, Private Secretary to His 

 Majesty the King, announcing that His 

 Majesty had been pleased to present to 

 the Royal Society a medal which was 

 struck in commemoration of -the Corona- 

 tion. The medal was inspected by the 

 members of the society. Also a medal com- 

 memorating the vist of Mr. Chamberlain 

 to South Africa, presented by Mr. A. But- 

 tei-field, jeweller. 



Exhibits. 

 On the itable was an interesting speci- 

 men of slickenside ore, from South Lyell 

 mine; also some of the fish referred to in 

 the secretary's notes. 



Papers. 

 A geological excursion to Port Cygnet in 

 connection with the Australasian As- 

 sociation for the Advancement of 

 Science, 1902. 



By W. H. Twelvetrees, F.G.S. 

 The author describes the visit of mem- 

 bers of section C (geology) of the A.A.A.S. 

 to Port Cygnet in January, 1902. The spe- 

 cial object orf the excursion Avas to examine 

 the elseolite syenite, tinguaite, and allied 

 rocks of the alkali division, which have 

 aroused initerest in geological circles in 

 Australia. The rocks occur as a zone 

 traversing the country near Lovett in a 

 N.E. — S.W. direction, and emerging on 

 •the shores of d'Entrecasteaux Channel at 

 Oyster Cove. They are broken through by 

 the mesozoic diaBase, which is prolonged 

 southwards from Mount Wellington, and 

 in «:heir turn they intrude into sedimen- 



tary strata of Penno-carboniferoiis age. 

 Their probable age is tJie close of the 

 Permo-Carboniferous. At the regatta 

 ground, Port Cygnet, a projecting head- 

 land was found to consist of eleeolite and 

 alkali syenite, with dark differenoated 

 margins of jacupira^ngite, essexite, and 

 uephelinjte. These marginal varieties are 

 not separated from the madn mass of 

 syenite, buc are produced by impercep^^ible 

 variations, the result of differentiation of 

 •the magma. As affording illustrations of 

 differentiation, the Port Cygnet area is 

 destined to become classic. A type collec- 

 tion of the rooks was forwarded to the 

 great German master in petrology. Pro- 

 fessor H. Rosenbusch, Avho has furnished, 

 with his usual kindness, valuable identifi- 

 cations of the rarer varieties. The por- 

 phyries of Mount Livingstone were recog- 

 nised by him as elseolite syenite porphyry,- 

 and the basic differentiation products of 

 the eiaeolitiic magma of the regatta ground 

 receivejj from him tljeir proper diagnoses, 

 though he confesses that some of the 

 varieties do not exactly correspond with 

 any of the alkali rocks known to him. The 

 presence of hauyne or nosean in the Mount 

 Livingstone elseolite syenite porphyry is 

 confirmed. In the mica si'jlvsbergite south 

 of che regatta ground Professor Rosen- 

 busch detected a mineral of the pyroch- 

 lore group, and he suggests that the sand 

 of creeks flowing over the jacupirangite 

 syenite at Regatta Point be examined for 

 the interesting mineral, baddeleyite 

 (dioxide of zirconium). These intrusive 

 rocks carry pyrites, and alo'ag the lines of 

 their contact with the sedimentary straca 

 some silification has taken place. Some 

 of the contact stone assays ooz. to 6az. of 

 silver, and from ^dwt. to 2dwt. or 3dwt_, 

 gold per ton. The district has yielded 

 about 3,000oz. alluv.a: gold, most of Avhich 

 was v/ou on the S'mall fiats near Lyming- 

 ton. The variations which distinguish 

 the Port Cygnet rocks from alkali rocks 

 elsewhere may be appealed to in illus«:ra- 

 tion of the theory of petroiogical pro- 

 vinces. Possibly new name- may be re- 

 quired for some of them. The study of 

 the group is not complete, but at present 

 the author arranges it as follows: — 



Family 1.— Alkali Granice: not repre- 

 sented. 



Family 2.— Alkali Syenite : Quar-tz augite 

 Syenite.' Alkali Syenite. 



Family 3.— Elseolite Syenite: Elseolite 

 Syenite, Elreolite syenite porphyry. Mica 

 solvsh'rgiti. Siilvsbergite porphyry. Tin- 

 guaite porphyry. Jacupirangi-te. 



Family 4.— Essexiite: Essexite. 



Family 5.— Theralite : Mica-nephelinite. 



Family 6.— Ijolite: not represented. 



