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Abstract

THIS book appears to supply a real want among students of that now very popular subject of study, microscopic petrography. Many of the existing text-books, which are for the most part written in German and French, demand a larger acquaintance with the principles of crystallography and physical optics than many students of the subject possess. Mr. Rutley evidently possesses a considerable experience of the wants of students, and is familiar with the kind of difficulties which prove most troublesome to them. With the greatest patience he endeavours to remove these hindrances to their progress, pointing out the different senses in which the same term is sometimes employed, cautioning them against prevalent misunderstandings, and advising them as to the best method of forming just conceptions concerning the abstruse problems with which they have to deal. Very noteworthy and excellent are the numerous drawings, which, though severely diagrammatic rather than pictorial, are admirably suited for their object. The student who follows the advice of the author, and by the aid of card-board, cork, and pins, constructs a series of models based upon these drawings, will be able to realize the essential peculiarities of the several mineral species in a way that no amount of description will enable him to do. In the general arrangement of this book, Mr. Rutley has followed the same excellent plan as Prof. Rosenbusch in the first volume of his excellent “Mikroskopische Physiographie.” The first part of the book, comprising 104 pages, is devoted to general considerations, and the second part (144 pages) to a description of the crystallographic and optical peculiarities of the chief rock-forming minerals, these being grouped according to their system of crystallization. In every part of the book there is evidence of the most painstaking care and conscientious attention to accuracy of detail, and we can heartily recommend the book to those who seek for just such an amount of information on optical principles as will enable them to employ the modern refined methods of petrographical research.