SOME NEW BOOKS. 



Crystals : Their Shape and Structure. 



Crystallography ; A Treatise on the Morphology of Crystals. By N. Story- 

 Maskelyne, M.A., F.R.S. 8vo. Pp. xii., 521. 398 text figures and 8 plates. 

 Oxford : The Clarendon Press, 1895. Price 12s. 6d. 



The appearance of a treatise on crystallography from the pen of 

 Professor Maskelyne, the doyen of English Crystallography, has been 

 expected for many years. The present volume deals only with a very 

 confined branch of the subject, i.e., that which concerns the relations 

 between the various planes bounding a crystalline individual ; a. 

 succeeding volume treating of the physical properties of crystalloid 

 matter is, however, promised. Two proofs of most of the propositions 

 are given, a trigonometrical and an analytical one ; the former are, in 

 many cases, those contained in Miller's classic " Tract," and although 

 very simple and elegant, are often long and possessed of all that 

 cumbrousness which so frequently characterises trigonometrical 

 demonstrations. The analytical proofs, many of which are new, are 

 extremely neat, and have the great merit of brevity. It is, perhaps, 

 to be deplored that the author should have confined his attention so 

 closely to the Millerian methods of demonstration, as many crystallo- 

 graphic problems can be treated with greater ease by other methods ; 

 thus, the long arguments at pp. 58 and 70 respecting the anharmonic 

 ratios of four tautozonal planes would surely be well replaced by the 

 short proof recently given by Cesaro. 



Not the least valuable portion of the volume is that dealing with 

 the methods of representing a series of crystalloid planes, in which 

 that crystallographic pons asinorum, the stereographic projection, is 

 elaborately treated. The chapter relating to the types of crystalline 

 symmetry is also one of extreme interest, owing both to the simphcity 

 and originahty of the treatment adopted. Professor Maskelyne has 

 here exercised his peculiar faculty for the invention of new and 

 significant terms, a faculty which is so freely employed in the later 

 part of the book as to make it a matter of regret that a glossary has 

 not been appended. The description of the crystalline systems is 

 clear and concise, and the characteristics of each are logically 

 deduced, thus ehminating that flavour of empiricism which taints 

 most of those dry-bone hashes known as text-books of crystallography. 

 The method employed is, however, in our opinion, not logical enough, 

 as it is now comparatively easy to deduce the thirty-two possible 

 crystalline systems by the rational process devised by Gadolin, or to 

 briefly indicate how this number is arrived at by the discussion of point- 

 systems and space lattices. This part of a crystallographic treatise 

 would thus be relieved of such a defect as that on p. 345, where milk- 

 sugar is described as crystallising in an impossible system. The 



