50 



NA TURE 



[May 1 6, 1907 



THE PROBLEM OF CRVST.ILLISATIOX. 

 .Ill Introduction to Chemical Crystallography. Bv 

 P. Groth. Authorised translation by Dr. Hutch 

 Marshall, F.R.S. Pp. xii+ X23. (London: Gurney 

 and Jackson, igo6.) Price 4^. net. 



IN providing for English-speaUing readers a trans- 

 lation of Prof. Groth's " Einleitung in die 

 chemische Krystallographie," Dr. Marshall has per- 

 formed a task of great utility, the value of which is 

 no doubt enhanced to many in this country by the 

 references to abstracts and papers in the Journal of 

 the Chemical Society added by him. In preparing 

 the translation he has kept closely to the original, 

 but not so slavishly as to mar the literary stvle. 



The question as to the precise nature of the con- 

 stitution of unorganised matter, including as it does 

 the problem of the phenomenon of crystallisation and 

 the relation between the chemical composition and the 

 crystal structure, has since the time of Lucretius, and 

 even earlier, been the subject of no little speculative 

 thought, much of which has necessarily been abortive 

 ■because the knowledge derived from experiment was 

 not sufficiently far advanced to act as a check on the 

 correctness of the various theories propounded. The 

 past century has, however, seen a vast increase in 

 the store of facts relating to the characters of mineral 

 substances, and chemists have, particularly in recent 

 years, recognised the importance of determining with 

 precision the crystallographical properties of the salts 

 prepared by them in the laboratory. For many years 

 past Prof. Groth has been engaged in the prepar- 

 ation of a complete digest of the physical properties 

 of all crystallised substances. The i^rst of the four 

 volumes in which that work will appear was reviewed 

 in N.ATLRE of .April 4 (vol. Ixxv., p. 529). To that 

 colossal work this small volume forms an introduc- 

 tion. 



In a remarkably brief compass, and with all his 

 ■customary lucidity of exposition. Prof. Groth has 

 summarised the state of our knowledge at the time 

 of writing. After a short discussion of the possible 

 varieties of crystal structure, he proceeds to consider 

 the main subject in its various aspects. Poly- 

 morphism deals with the various modifications dis- 

 played by the same substance, such as, to take the 

 best-known instance, sulphur, and the nature of the 

 transition between them. The next chapter is con- 

 cerned with morphotropy, or the comparison of the 

 crystal structures of chemically allied substances, 

 such as, for instance, the aromatic compounds. Iso- 

 morphism is a particular case of morphotropy, in 

 which the change in composition leaves the structure 

 almost unaltered. The last chapter treats of mole- 

 cular compounds, which, however, cannot be 

 differentiated from isomorphous mixtures. 



So vigorous is the growth of this subject that, even 

 though various alterations have been embodied in the 

 translation which were necessitated by the publication 

 of investigations during the short interval that elapsed 

 between the dates of appearance of the original and 

 the translation, further revision is demanded bv still 

 rs.ore recent material. Of primary importance is the 

 simple yet fundamental theory of close-packing put 

 NO, 1959, VOL. 76J 



forward by Mr. B.irlow and Prof. Pope in a paper 

 read before the Chemical Society in November last. 



\\"e may commend this introduction to all who 

 are interestt^d in this important subject, and especiallv 

 to chemists in this country, to whom we hope it mav 

 reveal the advantages of a study of crystallography, 

 a branch of science of which they are said to be 

 neglectful. 



PHYSICS FROM MANY POIMS OF VIEW. 

 (i) First Year's Course in Practical Physics. By 

 James Sinclair. Pp. viii4-i24; illustrated. (Lon- 

 don : George Bell and Sons, 1906.) Price is. 6d. 



(2) Theoretical and Practical Mechanics and Physics. 

 By A. H. Mackenzie. Pp. xvi4-ii2; illustrated. 

 (London: Macmillan and Co., Ltd.; New York: 

 The Macmillan Co., 1906.) Price js. 



(3) Junior Experimental Science. By \V. M. Hooton. 

 Pp. viii + 260; illustrated. (Cambridge: University 

 Tutorial Press, Ltd., 1906.) Price 2x. 6d. 



(4) Text-hook 0} Mechanics. By Louis .\. Martin, 

 jun. \'ol. i. Pp. xii+142; with diagrams. (New 

 York : John Wiley and Sons ; London : Chapman 

 and Hall, Ltd., 1906.) Price 5^. 6d. net. 



(5) The Tutorial Physics. Vol. v. Properties of 

 Matter. By C. J. L. Wagstaff. Pp. iv + 25i; illus- 

 trated. (Cambridge : University Tutorial Press, 

 Ltd., 1906.) Price 3^. 6d. 



(6) Practical Physics. By W. R. Bower and J. 

 Satterly. Pp. xi4-399; illustrated. (Cambridge: 

 LIniversity Tutorial Press, Ltd., 1906.) Price 

 45. 6d. 



(7) The School Magnetism and Electricity ; a Treatise 

 for Use in Secondary Schools and Technical 

 Colleges: hased on Potential and Potential-gradient. 

 By Dr. R. H. Jude. Pp. vi4-403; illustrated. 

 (Cambridge: University Tutorial Press, Ltd., 1906.) 

 Price 3^. 6d. 



(S) Mechanics Problems for Engineering Students. 

 By Frank B. Sanborn. Second edition, revised and 

 enlarged. Pp. viii-i-194; illustrated. (New York: 

 John Wiley and Sons ; London : Chapman and 

 Hall, Ltd., 1906.) Price r>s. 6d. net. 



(9) A First Course in Physics. By Dr. R. A. Millikan 

 and Dr. H. G. Gale. Pp. viii4-4S8; with illustra- 

 tions. (Boston, New York, Chicago, and London : 

 Ginn and Co., n.d.) Price 55. 6d. 



ANYONE who thinks that the existing supply of 

 text-books in mechanics and physics is quite 

 suflicient is neglecting to make an adequate estimate 

 of the extremely varied conditions under which 

 teachers and pupils work. There was never a time 

 when so much teaching was being done as now. 

 Elementary school, high school, public school, 

 technical school and college, each is developing on 

 different lines, with the result that each feels the 

 need of a text-book written specially to suit its w^ork. 

 Besides these, there is the cramming school, the main 

 object of which is to get a man " through " an ex- 

 amination ; this also has its special aims and needs, 

 and seeks to satisfy them. Those of us who are 

 ceasing to be young fared very differently in our day 



