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Abstract

THE task of introducing the student to any particular branch of science requires such selective judgment, such tact both in saying and in leaving things unsaid, that it is not surprising if many so-called “primers” fall short of the good intentions of their authors. Mr. Mawer, in this little book, presupposes “an acquaintance with the phenomena of pleochroism and the polarization of light,” and hence refers only in the briefest manner to the methods employed in the examination of thin mineral sections. He also, in his desire to be abreast of current literature, uses such terms as “allotriomorphic,” “micro-elsitic,” “magma-basalt,” without adequate definition on discussion; and in speaking of a “porphyritic ground-mass” he will throw many beginners into confusion. If the student is to seek elsewhere for instruction both in the manipulation of the polariscope and in the use of technical terms, the book must be held to fail in its fundamental object as a primer. It will probably serve well, however, to remind the learner of the broader features that mark out one rock-forming mineral from another. The author, moreover, insists, as befits a geologist, on the purely supplementary character of microscopic study—a warning that seems more than ever needed when micro-petro-graphy, by the change of a few letters, has been exalted to the level of a science.

Primer of Micro-Petrology.

By W. Mawer (London: Office of Life-Lore, 1888.)