712 PETROLOGICAL ABSTRACTS AND REVIEWS 



Tyrrell, G. W. "Further Notes on the Petrography of South 

 Georgia," Geol. Mag., Ill (191 6), 435-41. 



Describes various rocks from South Georgia. The sediments are slates 

 and phyllites, arkoses and grits. The igneous rocks are epidorite, dolerite, 

 basah, alaskite, quartz-felsite, lavas and tufifs of doubtful affinities, epidosite, 

 and augitite. So far as petrographic evidence goes, the question whether South 

 Georgia belongs to Suess ' " Southern Antilles, " or whether it is a remnant of an 

 old sunken continental land remains unsettled. 



Tyrrell, G. W. "The Petrography of Arran," Geol. Mag., Ill 

 (1916), 193-96. 



Pitchstone xenoliths in a basalt dike throw some Ught upon the ques- 

 tion of the temperature of lavas. The phenocrysts of quartz have suf- 

 fered hardly at all, the andesine has had a softening on the margins 

 and fissuring in the interiors, while the orthoclase shows fusion around the 

 margins and along cleavages, producing a yellow or grayish glass, differing from 

 that of the groundmass. The temperature of the intruding lava is therefore 

 thought to have been between 1170° C. and 1375° C. 



Tyrrell, G. W. "Some Tertiary Dykes of the Clyde Area," 

 Geol. Mag., IV (1917), 305-iS, 350-56, figs. 3. 

 Describes a dike-rock consisting of phenocrysts of anorthite in a ground- 

 mass of labradorite, enstatite and augite, and much glass. The glass indicates 

 orthoclase, silica, and albite. Chemically this rock approaches andesite, from 

 which it differs in its more basic phenocrysts. It is here called Cumbraite. It 

 differs from Thomas and Bailey's Inninmorite in containing enstatite as well 

 as augite. While the name cumbraite is proposed by Tyrrell, he says: 

 "Whether these terms should obtain a circulation outside the discussion 

 of the British Tertiary petrographic province is a question beyond the scope 

 of this paper. My own opinion is that they should not." 



Tyrrell, G. W. "The Trachytic and Allied Rocks of the Clyde 



Carboniferous Lava-Plateaus," Proc. Roy. Soc. Edinburgh, 



XXXVI (191 7), 288-99. 



Among the lavas of the Scottish Carboniferous, true andesites and rhyolites 



are absent, trachyte and allied rocks are present in subordinate quantities, 



while basalts predominate. In this paper are brief descriptions of albite- 



bostonites, albite-trachytes, albite-keratophyres, bostonites, keratophyres, 



quartz-keratophyres, felsite, and phonolite. Ten analyses, one of bostonite 



previously unpublished, are given. 



