CONTENTS. 



CHAPTER I. 



INTRODUCTION : Reasons for undertaking this work nature of its con- 

 tents its objects twofold. The study of the primary rocks long 

 neglected beginning to attract greater attention the proposed order 

 of arrangement Page 1 



CHAPTER II. 



DESCRIPTION OF THE GRANITIC ROCKS OF CORNWALL. 



Definition of the term primary, as here employed. General aspect of 

 primary districts. The present nomenclature of the primary rocks de- 

 fective. The ternary compound of felspar, quartz, and mica, the type 

 of granitic formations; its varieties. Excess of felspar, and the ac- 

 cession of shorl ; the characteristics of the Cornish granitic formation. 

 The different kinds of Cornish granite: shorl-rock, protogine, eurite, 

 felsparite, and the quartzose varieties of these rocks, or quartz-rock. 

 These granitic rocks associated together, as alternating beds, as irregular 

 imbedded patches or masses, as veins, as el vans or dykes - 7 



CHAPTER III. 



THE GRANITIC ROCKS OF OTHER COUNTRIES COMPARED WITH 

 THOSE OF CORNWALL. 



Descriptions of these rocks neither numerous nor circumstantial. The 

 granite of Aberdeenshire characterised by its hornblende its varieties. 

 The association of granite and porphyry in the mountain Cruachan 

 and of granite and quartz-rock near Glen Tilt. The granitic district 

 of the eastern part of Ireland it abounds in quartz and is cha- 

 racterised by mica. Granitic rocks of the Erzgebirge, at Freyberg, 

 Altenberg, and Zinnwald. Granite of the Hartz mountains also 

 micaceous its nature doubtful interstratified with schistose rocks. 

 Remarks on the binary compounds of quartz with shorl, mica, or 

 talc V - ' *- - - - 24- 



