112 GEOLOG\ OF THE HIGH PLATEAUS. 



The foregoing scheme of classification is in the following conspectus 

 given as a whole. Of the various sub-groups the following have not yet 

 been detected among the eruptives of the High Plateaus : nevadite, por- 

 phyritic trachyte, augitic propylite, dacite, nephelin-dolerite, leucite-basalt, 

 nephelin-basalt. All of the others are well represented. The trachytic 

 group, however, very far overshadows all the others in volume and variety. 



Geoup I. — Acid books. Khyolites. 



Sub-groups. 



1. Nevadite. 2. Liparite. 3. Ehyolite (proper). 



Geoup II. — Stjb-acid books. Trachytes. 



Subgroup A. — Sanidin trachytes. Sub-group B. — Hornblendic trachytes. 



1. Granitoid trachyte. 5. Hornblendic trachyte. 



2. Porphyritic trachyte. 6. Augitic trachyte. 



3. Argilloid trachyte. 7. Phonolite. 



4. Hyaline trachyte. 8. Trachytic obsidian. 



Geoxip III. — Sub-basic bocks. Andesites. 

 Sub-groups. 



1. Hornblendic propylite. 4. Hornblendic andesite. 



2. Augitic propylite (?). 6. Augitic andesite. 



3. Quartz propylite. 6. Dacite. 



Geoup IV.— Basic bocks. Basalts. 

 Subgroups. 



1. Dolerite. 4. Leucite basalt. 



2. Nephelin dolerite. 6. Nephelin basalt. 



3. Basalt (proper). 6. Tachylite. 



