124 



E. 0. Teale 



Here again, however, many more sections require to be examined' 

 in order to deterniine whether in their case, as it would seem to- 

 be, the orthocbise felspar predominates. 



Chemicfil Choracfern avd Pefro()ia pliical Heldfio/is/iijis. — Onlv a 

 few analyses are available, and from a limited area. These are all 

 of the acid rocks; none have yet been made of the andesitic types. 



Makings use of the instructive variation tables given by Summers- 

 (•33, Fi*r. 3, p. 270), it is seen that th.e important types of Devonian 



N' 8. 



Brogger Diagrams 



Dacife, Brdemar House. Mac'cd on. 



(^SWcits ^nd Summers) ' 



G ranodionre , Br,iem>ir House,Mjcedon.. 



(^SKwts.inJ Summers), 

 N'i7. 



Fiq 3. 



Sfrinilc, GiSbo Island 



(SiirnmerSj 33.) 



Ffcj 4. 



QudrL'-Porph^nte^Tfirji R<inqe 

 ^^Spcc.ioo. ,/ln<il..Thielel 



Fia 5. 



Rhyohre, M'^Wellinofon 

 ( Anal .Thicltr) 



Qudrlz-Cerafophyrc , Nowj Now.^. 

 (Spec,63.Awl-ThiEle) 



