Chemistry and Physics. 679 



this little book my son and I have first made an attempt to set 

 out the chief facts and principles relating to X-rays and to crys- 

 tals, so far as they are of importance to the main subject." " We 

 have devoted the remaining and larger portion of the book to a 

 brief history of the progress of the work, and an account of the 

 most important of the results which have been obtained." 



A more detailed idea of the contents of this most opportune 

 volume may be derived from the titles of the chapters, which are: 

 "I Introductory, II Diffraction of Waves, III The X-Ray 

 Spectrometer, IV The Properties of X-Rays, V Crystal Struc- 

 ture, VI X-Ray Spectra, VII The Analysis of Crystal Structure I, 

 VIII The Analysis of Crystal Structure II, IX The Relation 

 between Crystal Symmetry and the Arrangement of the Atoms, 

 X The Analysis of Crystals III, XI The Intensity of X-Ray 

 Reflection," and " XII The Analysis of the Laue Photographs." 

 The value of the text is greatly enhanced by the fact that its 

 authors have both contributed largely to the progress of the sub- 

 ject and that W. L. Bragg has greatly simplified and illuminated 

 the crystallographic problems by his conception of " reflecting " 

 planes of atoms. r h. s. u. 



8. Elementary Chemical Microscopy ; by Emile Monnin 

 Chamot. Pp. xiii, 410, 139 figures. New York, 1915 (John 

 Wiley and Sons, Inc.). — In the opinion of the author the advan- 

 tages to be derived from the intelligent use of the microscope 

 have been largely neglected or overlooked by the American 

 chemist. Among the various causes which have conspired to 

 produce this condition, the two which stand out most prominently 

 are (i) lack of appreciation of the fact that a great variety of 

 problems are solvable by means of the microscope, and (ii) the 

 non-existence in English of an elementary but adequate text- 

 book on the subject. The present volume is derived primarily 

 from the mimeographed sheets which the author has written for 

 his classes during the past fifteen years and it is designed to close 

 the gap in the literature of the subject. As regards preliminary 

 training the author says : " It is assumed that the students for 

 whom this textbook is intended have had a course in crystal- 

 lography and one in physics, including optics." 



The first chapters are devoted to detailed descriptions and 

 explanations of the manipulation of such pieces of apparatus as 

 oculars, objectives, illuminating devices, ultramicroscopes, metal- 

 lurgical microscopes, accessories, radiants, micrometric micro- 

 scopes, polarizing systems, etc. " The instruments figured (and 

 the methods described) have all been tested and tried by the 

 author with but one or two exceptions." The remaining chap- 

 ters deal with the practical applications of the methods and appa- 

 ratus previously considered. In particular, pages 273 to 382 per- 

 tain to characteristic microchemical reactions of the common 

 elements and acids when in simple mixtures. The last chapte r 

 deals with the preparation of opaque objects for the microscopi 

 study of internal structure. In many cases the names of th 



