GNEISS. 255 



nearly continuous ; and, as the quartz and the 

 felspar are the predominant substances, it is 

 marked by considerable peculiarity of aspect ; 

 particularly when, as is not unfrequent, the for- 

 mer is white and the latter red, or when their 

 colours are in any other manner strongly con- 

 trasted. When perfect, the laminar variety pre- 

 sents no trace of a granular structure ; but it 

 passes into both of the preceding, and thus loses 

 its definite character. Although so decidedly 

 laminar in composition, it is far less fissile than 

 the preceding variety. 



In composition, gneiss fundamentally resem- 

 bles granite ; or, the prevailing minerals which 

 enter into it are quartz, felspar, mica, and horn- 

 blende. To describe the mode in which these 

 are combined, would be merely to repeat that 

 which has already been said under the head of 

 granite. 



But there is one important variety in which 

 compact felspar forms an essential and conspi- 

 cuous ingredient, and to which granite affords 

 no parallel. That rock has been without scruple 

 ranked in this division, because it accompanies 



