294 PROCEEDINGS OF SECTION C. 
orthoclase, microperthite, anorthoclase, arfvedsonite, rie 
beckite, barkevikite, egirime, and egirine-augite—often 
sodalite and nepheline. Soda trachytes are their effusive 
equivalents. 
Before passing to the very distinctive and complex group 
of nepheline rocks, which are developed in great variety at 
Port Cygnet, it will be well to consider briefly our aberrant 
members of the system. Keratophyres and quartz-kerato- 
phyres (soda-felsites and soda quartz-felsites) are recognised 
as effusive forms of alkali-syenite and alkali-granite. They 
occupy, however, an abnormal position, in that they have 
always been found hitherto associated with diabase or 
“diorite, and not, as might have been expected, with alkali 
rocks. In Tasmania they form no exception to the rule as 
regards any connection with elzolitic rock-masses. The 
nearest rocks with which they can be said to have any con- 
nection are the quartz-porphyry and pyroxene-quartz por- 
phyry of the West Coast. 
A zone of greenish felsitic rock, sub-schistose in aspect, 
flinty and often red-streaked, passes north and south along 
the western slope of Mt. Read, conformable to and enclosed 
in the copper and silver-lead-zinc sulphidic schists for which 
that mountain is famous. It has been traced north to Mt. 
Black as far as the Pieman River. It is doubtful whether 
the copper-bearing rock at the Hawkesbury and Cutty Sark 
on Mt. Black is not a micro-granitic modification of it. A 
rather singular feature is, that at Mt. Read it is non- 
metalliferous. The rock is greatly obscured by age and 
metamorphism, but ics microscopic examination shows pla- 
gioclastic felspars to be abundant. This gave rise to the 
suspicion that it might be a member of the small group of 
soda felsites (in their metamorphosed, sheared form often 
termed porphyroids). Professor H. Rosenbusch, after 
examining specimens sent to him, wrote with his character- 
istic good nature, as follows: —‘‘ Undoubtedly we have here 
strongly dynamically altered forms of che acid eruptive 
rocks. The typical porphyritic structure, the nature of the 
phenocrysts, the still recognisable fluidal structure, the 
nearly entire absence of dark constituents, the occasional 
spherulitic forms still recognisable in their replacement pro- 
duccs (quartz-albite), all point with certainty to members of 
the quartz-porphyry family; and, with great probability, 
not to quartz-porphyry in the narrower sense, but to quartz- 
keratophyre and keratophyre . . . The rocks greatly 
resemble our German occurrences in Westphalia, the Fich- 
telgebirge, and Thiiringen, and especially the occurrences 
