KiNAHAN — On Granitic and other Inyenite Mocks. 103 



Paet I. 



JRoclc-names and general description. 



The ingenite rocks of this area include Plutonic rocTcs (Basic and 

 highly Siliceous) ; Metamoriiliic rochs (Sedimentary and Igneous), and 

 Granitic rochs. 



General Table of the RocTcs. 



PiiTTOXic Rocks. — Carhoniferous (?) Whinstones ; Post-silwian' 

 Wliinstones ; Llandovery WTiindstones ; Pre-Llandovery Whinstones ; 

 Camhro-silurian (?) Whinstones (Metamorphic) ; Post-silurian Fel- 

 stones; Silurian Felstones (Llandovery age) ; Pre-LlandoveryFelstones ; 

 Camhro-silurian {?) Felstones (usually Metamoi-phie). 



!META3roRPHic EocKS. — Schist, including schistose-limestone, schis- 

 tose-dolomyte, ophyte, and steatyte ; Gneiss; Sornhlende rock'^'' (meta- 

 moi'phic whinstone) ; Foliated Felstone or Gneissyte and Granitoid 

 Felstotie (metamorphic felstone). 



Gkaxitic Eocks. — Elranyte or Quartz Porphyry ; Oligoclasic] Gra- 

 nite; Orthoclasic or Highly Siliceous Granite. 



Plutoxic Eocks. I — In the foregoing list the oldest whinstones and 

 felstones, except a few of the latter, are more or less metamorphosed ; 

 consequently they do not note belong to the plutonic rocks and cannot 

 be described among them, but their descriptions will be found among 

 the metamorphic rocks, under the names, Hornhlende rocTc, Gneissyte, 

 and Granitoid Felstone. They are enumerated in the list to show 

 their age and origin. 



Whinstones. — The teim whinstoyie is here used in preference to 

 greenstone on account of the varied significations given to the latter. 

 Namnann confines the name to diabase ; Brongniart to dioryte (amphi- 

 bole 4 felspar, not orthoclase) ; Cotta includes in his greenstone group, 

 diabase and dioryte ; while Juices and many other British geologists 

 included not only all the basic-plutonic rocks or whinstones but also 

 many of the basic felstones (Eurytes of Daubuisson), especially if the 

 latter are of a green colour. 



Pre-Llandovery Whinstone. — These rocks seem principally if not 

 wholly to belong to the group of rocks that are included under the 

 general name of diahase [pyroxene (diallage generally) + felspar (not 



* This term is used as Macciilloch iised it. 



t These granites were originally called oHgoclasic granites, as the waxy felspar 

 was supposed to be oligoclase ; now, however, by microscopical examination, it is 

 found to be in part orthoclase, probably adularia. The names, however, may still 

 stand, as oligoclase seems to be an essential element of the rocks, while it is rare 

 in the orthoclasic granite. \_Note while in prcssP\ 



\ From I'iutns, the god of the infernal or lower regions, the name having been 

 given to these rocks in contiadistinction to the volcanic rocks or those fonned at or 

 near the present surface of the earth. 



