GNEISS, 263 



THIRD DIVISION. 



Of irregular composition, being either defi- 

 ient in the number of ingredients required to 

 meet the definition of gneiss, or containing some 

 substance not included in that definition. 



A. Quartz and felspar; simply laminar and at 

 the same time granular. The foliated disposition here 

 results from the crystalline position of the felspar* 



B. Hornblende and felspar, foliated and some- 

 times imperfectly schistose. Analogy and geological 

 connexions claim a place here for this rock; it is how- 

 ever the primitive greenstone of some, and the horn- 

 blende schist of other authors. It is also described 

 under the head of hornblende schist, 



C. Felspar and mica. Lewis, &c. 



D. Felspar and clay slate. Isla, Lewis. 



E. Felspar and chlorite schist, Gigha, Sky, 



F. Felspar, quartz and chlorite schist. Sky. 



G. Felspar, quartz and clay slate. North Uist. 

 H. Felspar, quartz and talc. Seal pa, (West.) 



I. A granular mixture of felspar and quartz in 

 one lamina and clay slate in another, 



K. The same with chlorite schist instead of clay 

 slate, Sky, 



L. The same with grey wacke schist, ditto. 



M. Compact quartz with imbedded grains of fel- 

 spar, in one lamina, and the same schists in the other. 

 Sky. 



