CONTEXTS. vii but common to the whole mass. — The general structure dependent on the aggregation of individual concretions. — The layers of granite pos sessed of determinate bearings like strata. — Structure of the'primary schists. — The nature and disposition of strata. —The curvatures and convolutions in the beds of primary rocks. — Their angular and sphe roidal structure, resembling breccia and conglomerates - Page 91 CHAPTER VII. ON THE RELATIVE POSITION, AND ON THE NATURE OF THE GRANITIC AND SCHISTOSE ROCKS AT THEIR JUNCTION. Position of the primary schists next granite. — They extend far over this rock, through the transverse valleys in Cornwall. — The mica-slate of Ireland similarly situated, capping the granitic mountain of Lugnaquilla.— The Cornish strata skirt the granite in an irregularly undulating curve.— The same arrangement obtains in the Isle of Arran,—in the north of Scotland,—and in the Alps.—Dip of the strata at the junction,—in Arran,—in Cornwall,—in Galloway,—apparently irregular—not so — dependent on the structure of the primary rocks — illustrated by sections. -—The anticlinal axis of primary districts — said to be simple in each geographical range—not so in the Ocrynian range, nor in the Pyrenees. — Composition of granite and primary schists at their junction — in Corn wall,—near Cherbourg,—in Ireland,—in Iona and Mull,—in Glen Tilt,—and near St. Paul de Fenouillet in the Pyrenees - - 119 CHAPTER VIII. ON THE VARIOUS MODES IN WHICH THE GRANITIC AND SCHIS TOSE ROCKS ARE ASSOCIATED TOGETHER. The occurrence of granitic rocks in the primary schists — in the form of beds or courses — in irregular bunches or masses—in Cornwall,— Scotland,—Ireland, — andNorway. — Portions of these schists also con tained in granite—in Cornwall,—in various parts of Scotland,—and in France. — The primary strata traversed by granite-veins — in Cornwall, —and in Scotland. — Summary of the various appearances presented by these veins - - - - - 143 CHAPTER IX. ON THE MINERAL AND METALLIFEROUS VEINS IN THE PRIMARY ROCKS. Our knowledge of veins very imperfect — and too hypothetical.— The definition of veins not correct. — The following details on this subject entirely'drawn from Cornwall.—Description of veins as seen on the sea shore, in quarries and similar open situations—of small or concretionary veins — of larger veins, not confined to individual rock-concretions, but traversing one or more lay'ers or strata. — These commonly called