326 Reviews — Prof. Slory-Maskelyne' s Crystallograpliy. 



that while the submergence may have been short, the succeeding 

 glaciation may have been — or rather, he seems to say, must have 

 been — long ; and as it continued, and " sub-glacial erosion " was 

 carried on, " the supply of shelly deposits at and below the level of 

 600 feet would tend to become exhaiisted, and the Boulder-clay 

 continually passing outwards from the land would eventually contain 

 no shells."^ This is our old friend, the theory of the "complete 

 sweeping-out by the second glaciation," which we humbly thought 

 had been disposed of some time ago,^ but of which, as it now comes 

 up again under the wing of Dr. Geikie, it is necessaiy anew to take 

 some cognizance. We think we can demonstrate (with Dr. Geikie's 

 help) the impossibility of the ice performing what is thus ascribed 

 to it. 



[To he continued.) 



la E "v I E -vsT s. 



I. — Crystallography, a Treatise on the Morphology of 

 Crystals. By N. Story-Maskelyne, M.A., F.K.S. Octavo, 

 512 pp., 398 figs., and 8 plates. Oxford, Clarendon Press, 1895. 



IN one of his scientific aphorisms Goethe pronounces criticism 

 upon Crystallography ; this science, he says, has about it some- 

 thing of the Monk and the Old Bachelor : it exists for itself alone, 

 it has no applications, it leads to no results ; and yet, he adds, it has 

 by some means captivated and retained its hold upon some of the 

 acutest intellects; this fact is due, he supposes, to the extent and 

 the complexity of its details, which supply almost inexhaustible 

 material for the active mind. 



The criticism is no longer true. When Goethe wrote these words 

 the geometrical principles of Crystallography, now known to be 

 remarkably simple and definite, had not been fully established ; 

 outside pure Mineralogy its applications at that date were indeed 

 few. But now the Monk has called upon his neighbours, and the 

 Old Bachelor flirts with the spinster sciences — with Geology and 

 Chemistry in particular the most friendly relations have been 

 established, and Petrology, the result of the former liaison, is a 

 young science fast growing to robust maturity. 



Whether they wish it or no, a large proportion of modern 

 geologists must acquire some knowledge of Crystallography, without 

 which the study of rocks is almost impossible. Maskelyne's 

 " Morphology of Crystals " will not, it is true, satisfy all their 

 requirements, because it does not deal with the optical and other 

 physical characters, but it is, and must long remain, the standard 

 book to which the geologist must turn for information about the 

 geometry of the subject. 



Beginning with the later portions of the book, the reader will find 

 in chapter viii an account of the manner in which crystals are 

 jneasured ; the preceding chapter contains a detailed account of the 



1 p. 142. 2 Trans. Geol. Soc. Glasgow, vol. ix, pp. 109, 110. 



