418 Revieics — A. Johnstone' s Minerahgical Geology. 



III. — MiNERALOGicAL Geology : A Stnopsis for the use of 

 Students ; to accompany W. and A. K. Johnston's Geological 

 Map of the British Isles. By Alexander Johnstone, F.G.S. 

 8vo ; pp. 194, with 12 plates of fossils. (Edinburgh and 

 London : W. & A. K. Johnston, 1897. Price 3s. Qd. separate ; 

 or 23s. Qd. with the Map, which is reviewed on p. 417.) 



THE Geological Magazine for March, 1865, contained a notice 

 of the " Outlines of the Geology of the British Isles," accom- 

 panying Johnston's Geological Map. Since then our knowledge of 

 the geological details has been improved by the Geological Surveyors 

 and others, for the newer editions of the map ; and the study of 

 rock-structure, or lithology, has increased so widely and earnestly 

 that it has become as necessary as palasontology for the right 

 interpretation of the succession of sti-ata. their relative age and 

 modes of origin. Of course a knowledge of mineralogy must 

 precede a perfect acquaintance with the structure of rocks ; 

 and, indeed, the earlier geologists thought more of minerals than 

 of fossils. 



The author states that, as the distribution of minerals is not shown 

 on the Geological Map, he has thought it well to devote this book 

 specially to the consideration of the mineral side of the science. He 

 proceeds to a systematic treatment, first, of the common elements, 

 and, secondly, of the common compounds, occurring in the crust of 

 the Earth : and then advances to the exposition of mineralogy, 

 including crystallography. For the character and conditions of 

 minerals, pages 15-110 are apportioned. Systematized descriptions, 

 with useful tables for comparisons and contrasts, give full details 

 of each property, feature, and condition ; microscopic treatment being 

 referred to when necessary. 



In Section III, pages 110-179, is given an alphabetical catalogue of 

 the most important minerals, with concise notes as to their chief 

 characters and their British localities. A Table of the Igneous 

 Eocks succeeds (pp. 180-191) ; useful both in general and special 

 aspects. The Aqueous a»d Metamorphic Eocks are succinctly 

 tabulated. 



Fossils, after all, are not neglected. A neat table shows the 

 range-in-time of the most important animal forms, as they occur 

 in the successive geological systems or formations; and is accom- 

 panied by twelve plates illustrative, to some extent, of the several 

 zoological groups, from the Corals upwards, for the Palgeozoic, 

 Secondary, Tertiary, and Quaternary systems. 



There is altogether a great store of mineralogical information, 

 compendious, well-planned, and easily got at, in this valuable little 

 book ; besides its condensed and illustrated paleeontological appendix. 

 Probably, however, the students for whom this " Mineralogical 

 Geology " seems to have been specially intended would wish that the 

 plates had figures of minerals and rock-structures as well as fossils. 



