VI CONTENTS. 



CHAPTER IV. 



DESCRIPTION OF THE PRIMARY SCHISTOSE GROUP OF CORNWALL. 



The division of the primary rocks into stratified and unstratified ob- 

 jectionable. Proposed to divide them into granitic and schistose 

 groups only an artificial arrangement to facilitate description. 

 Primary slates enumerated. Schistose group of Cornwall. Consists 

 of two series, the porphyritic and the calcareous. Definition of these 

 series. The slates next the granite variously named by Geologists. 

 They are of a peculiar nature. Of two kinds one bounding the 

 eastern granite, the other the western. They pass into other kinds of 

 slate. The nature of this transition. Greenstone, actynolite-rock, 

 chlorite-rock, and the magnesian-rocks. Talc-schist, serpentine, and 

 euphotide, described. Remarks on the quartzose varieties of all these 

 rocks, commonly called quartz-rock. Nature and position of the gra- 

 nitic rocks or elvans, in the schistose group of Cornwall - Page 36 



CHAPTER V. 



DESCRIPTION OF THE SCHISTOSE ROCKS ASSOCIATED WITH 

 GRANITE IN VARIOUS COUNTRIES. 



Mica-slate and clay-slate of the eastern part of Ireland. Their alternations 

 with quartz-rock and hornblende rocks. Their associations with 

 granite. The composition of this rock, and its modes of arrangement. 



The gneiss formation of the Western Isles of Scotland. Its beds of 

 mica-slate, greenstone, compact-felspar, clay-slate, talc-schist, serpentine, 

 limestone, quartz-rock. The nature of their connection with each 

 other, and with the gneiss. Abounds in bunches and veins of granite. 

 Description of the primary schistose rocks of Norway, gneiss, mica- 

 slate, and clay-slate, with their subordinate beds. They contain im- 

 mense beds of granite, and are interstratified with smaller ones. The 

 primary schistose group of Saxony, gneiss, mica-slate, clay-slate, and 

 shorl-schist. The talcose formations of the Alps, including tal- 

 cose granite or protogine, talc-schist, serpentine, and other magnesian 

 rocks. Of the island of Corsica, composed of granite, eurite, proto- 

 gine, hornblende-rocks, euphotide, talc-schist, serpentine, and analogous 

 rocks - - 58 



CHAPTER VI. 



ON THE STRUCTURE OF THE PRIMARY ROCKS. 



Two kinds of structure, the internal and concretionary. Both of these 

 also admit a binary subdivision. The concretionary being either simple 

 or compound, and the internal structure either massive or fissile. 

 Structure of granitic rocks developed by the action of the elements 



can also be ascertained by cleavage. - Macculloch's remarks on the 

 spheroidal structure of granite. This structure not confined to blocks, 



