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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 elvans 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 - - - - - 2i