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Published online by Cambridge University Press: 01 May 2009
Under the general terms of Primary and Original, given by Werner and others, to the early crystalline rocks, have been included various mineral aggregates which may be classed under three heads: 1. The great stratiform masses of aqueous origin, essentially granitic, and formed by slow deposition at the earth's surface, which I have called Indigenous rocks. 2. Those lesser crystalline masses which were formed under similar conditions to the last, but within veins or fissures in pre-existing rocks, and may therefore be called Endogenous. 3. Rocks resembling the last in their geognostic relations, and often confounded with them, but distinguished by the fact that they have come into their present positions not by deposition from solution, but by displacement in a more or less fluid or plastic state. These Exotic or erupted masses, whether ancient or modern, are in a sense Primary, since they sustain, in one way or another, intimate relations to the more ancient rocks to which this name was first given.
page 493 note 1 Grundfjeldspsrofilet ved Mjφsens sydende, Nyt Magazin, 1885, p. 215.Google Scholar
page 493 note 2 Some modification in the use of the term clastic is rendered necessary by recent discoveries. I venture to suggest that it should be applied to all rocks which consist largely of mineral fragments and that we should distinguish between the three types of clastic rocks at present recognized by using the terms epiclastic, cataclastic, and pyroolastic. Epiclastic–Rocks formed of fragments resulting from the breaking up of older rocks occurring upon the earth's surface. Cataclastic—Rocks largely composed of fragments produced during the deformation of older rocks by the earthstresses. Pyroclastic—Fragmental rocks of volcanic origin. The same terms may he applied to the structures which characterize the rocks in question.
page 498 note 1 Inasmuch as these distinctions were first devised and announced by the Canadian Geological Survey, it may here be said that its earliest printed reports on the ancient rocks of the country (those for 1845 and 1846, published in 1847) were prepared from Geological the notes and collections of Logan and Murray, by the present writer after his connection with that Geological Survey in February, 1847, and that all subsequent matters relating to lithology in its reports up to 1872, were either prepared by him or under his direction.