I go N. L. BOW EN 



By piecing together the information to be obtained from the 

 examination of such sequences and observation of the structural 

 relations of the minerals a conclusion as to the reaction series in 

 rocks is to be arrived at. Without going into detail as to the evi- 

 dence, an attempt is made below to arrange the minerals of the 

 ordinary subalkaline rocks as reaction series. Neither rigid accu- 

 racy nor finality is claimed. It is regarded merely as a framework 

 upon which others may build, making such modifications and 

 additions as may be found necessary. 



TABLE II 



Reaction Series in Sub-alkaline Rocks 

 olivines ^ 



o> calcic plagioclaees 



Kg pyroxenes g* / 



V calci-alkalic plagioclases 



Mg-Ca pyroxenes / 



\ alkali- calcic plagioclases 



/ 

 amphiboles / 



Valkalic plagioclase 



biotites / 



\ / 



potash feldspar 



1 



muscovite 



i 



quartz 



Beginning at the upper end of the series in the more basic 

 mixtures we have at first two distinct reaction series, the continuous 

 series of the plagioclases and the discontinuous series, olivines- 

 pyroxenes-amphiboles, etc. As we descend in these series, how- 



