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AO DESCRIPTION OF THE PRIMARY [Ch. TV. CHAPTER IV. description of the primary schistose group of CORNWALL. The division of the primary rocks into stratified and unstratified objectionable.— 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, the other the western granite. — 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 granitic rocks or elvitns, in the schistose group of Cornwall. The primary rocks have been divided into stratified and un stratified ; the latter comprising the various granitic rocks, which generally occur in large insulated clusters, and have a compact and massive structure; the former denoting those non-fossiliferous rocks which surround, and are intimately connected with the granite, and are very commonly distin guished by a slaty or schistose texture. It will be found, however, that this division is perfectly arbitrary; for both stratified and unstratified rocks are so intermixed in their associations, that it is sometimes impossible to decide to which of these classes a rock, under examination, belongs: in order, therefore, in some measure, to avoid this confusion, the primary rocks will, in the following pages, he supposed to consist of granitic and schistose groups; only understanding by this division, that in the one granites, and in the other slates predominate; and it must not be forgotten that this is an artificial, not a natural arrangement, merely to facilitate description.