l-v, 



.1. S. MI.IKi: — SANDSTONE DIKES. 



the latter case they sometimes contain glass inclusions, showing that the 

 grains are quartz phenocrysts derived from an eruptive rock, and may 

 have been made round in the original mass. The angular grains not in- 

 frequently contain the minute, dark needles commonly found in the quartz 

 nf' granitic rocks, [nclusions of magnetite, biotite, and zircon have also 

 been noticed. 



Both strial id and unstriated feldspar are present : sometimes they are in 

 about equal proportions, l»ur generally the plagioclase is most abundant. 



<-»--iA^\ 





4 



.-v, 



Fioork 5. 



Km. i in: G. 



I i.i i:i 7. 



I- - i,.i it i . -Mot ' Vital movent nt ■■< th< m to pro- 



tht folia. 



Fioi i:i •■. — /■ ird '• nt of tin 



I ■ i p< i /•< n I Hon. 



'I'lip biotite represented in figu tnd7 ir mewhat leas than half a millimeter 



in length. 



1 I casionally the feldspar is much altered. Inn elsewhere it is clear with but 

 Blight trace of alteration, and between crossed Nicola shows twinning bands 

 very distinctly. Like tin- quartz, tie- grains of feldspar are angular and 

 Bhow hnt little nt' tin- alna.-iiiii consequent upon beach action for a long time 

 nr t ransportat ion for a long distam 



