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Ch. II.J DEFINITION OF THE TERM PRIMARY. 7 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 defective. — The ternary compound of felspar, quartz, and mica, the type of granitic form ations : its varieties. — Excess of felspar, and the accession of shorl, the cha racteristics of the granitic formation of Cornwall. — 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. Before proceeding to describe the various primary form ations, it is desirable to define in what sense the word primary is here employed; and this is the more necessary, since it has not only fallen into disrepute both with foreign and British geologists, but attempts have been lately made to erase it altogether from the nomenclature, as conveying an idea incompatible with the prevailing theory. The term primary, in its original acceptation, is certainly very objectionable, inasmuch as it has a theoretical signi fication, which ought to be avoided in every classification: but the word hypoyene, by which Lyell has proposed that it shall be superseded, is liable to the same objection; and the term crystalline schists, advanced by Boue, though free from this defect, is not more happy, because several igneous and sedimentary rocks have a similar characteristic. For these reasons we have continued to use the word primary; but, at the same time, regret the want of such a term as would be generally applicable to rocks of this nature without implying any hypothesis. In the mean time, how ever, it is proposed, in the following pages, to consider as primary rocks the various kinds of granite, and all those B 4