PEATE eX. 
MICROSCOPIC STRUCTURE OF MINERALS AND ROCKs. 

1. Granophyric structure: minute intergrowth of Quartz and Felspar. Granophyre. 
crossed, 
2. Calcite, with rhombohedral twinning and cleavage. Marble. Nicols crossed. 
3. Trachytic structure: small crystals of Felspar in fluxional arrangement. Bostonite, 
crossed, 
4. Trachytic structure ; 
dine. Trachyte. Nicols crossed, 
[To face page 33. 
Nicols 
Nicols 
microlites of Welspar eddying round a group of larger erystals of Sani- 
igs 
