260 GNEISS, 



THFRD SUBDIVISION. Laminar. 



Each substance occupying a distinct lamina, 

 the quartz and the felspar being separated ; some- 

 times remaining in con tact, at others being divided 

 by intervening laminae of mica or of hornblende: 

 the quartz frequently puts on the muddy aspect 

 of chalcedony. 



A. Quartz and felspar in alternating 1 laminae : be- 

 longing, with D, strictly, to the third division, 



JB. Quartz, felspar and mica, similarly alternating. 



C. Quartz, felspar and hornblende, disposed ia 

 the same manner. 



D. Felspar and hornblende in alternating la- 

 minae* 



E. Quartz, mica and hornblende j the two latter 

 generally in one lamina. 



The varieties A, B, are abundant in Glen Elg, 

 Rona and Ardgower ; the third occurs occasion- 

 ally in various situations. The quartz is also 

 found alternating with mica only, or with horn- 

 blende only, in the same situations ; but it is 

 scarcely necessary to specify these varieties, as 

 they appear to be very limited in extent. 



In varieties C, D, the felspar often assumes a 

 very peculiar aspect; consisting of crystalline 



