THE closing years of the nineteenth century witnessed a revival of interest in the petrology of gneous rocks, which must be regarded as marking an important stage in the development of that subject.

THE second volume of Prof. Johannsen's work on petrography is both a descriptive petrography of the quartz-bearing igneous rocks and an illustration of the author's proposed new method of ...

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Introduction -- Physical properties of magma -- Intrusion of magma -- Forms of igneous bodies -- Cooling of igneous bodies and other diffusion processes -- Classification of igneous rocks -- ...