Introduction

Abstract

Petrology is the science of rocks, that is, of the more or less definite units of which the earth is built. In the nature of things the study is limited to the materials of the accessible crust, although we have in meteorites samples of rocks which must be identical with, or analogous to, those composing the interior of the earth. The science deals with the modes of occurrence and origin of rocks, and their relations to geological processes and history. Petrology is thus a fundamental part of geological science, dealing, as it does, with the materials the history of which it is the task of geology to decipher.