304 



NA EC/RE 



[September 2, 1922 



the one-circle, horizontal, reflecting goniometer, and 

 follows closely on the lines of the original edition. A 

 useful account of methods of goniometry at low 

 temperatures has been introduced ; and the use of the 

 two- and three-circle goniometers, and the methods 

 based on the gnomonic projection and associated with 

 the name of V. Goldschmidt, receive more adequate 

 treatment than before. The student will, however, 

 miss in this chapter the extraordinarily detailed 

 description of every step in experiment and in com- 

 putation to which Dr. Tutton has accustomed him in 

 what has gone before ; and when he finds that three 

 hundred pages are devoted to the discussion of one- 

 circle goniometry the enthusiast for two-circle methods 

 will scarcely perhaps feel content with part of one 

 chapter. Many readers will wish for fuller information 

 as to the methods of drawing crystals devised by 

 Penfield and by Goldschmidt, and would have welcomed 

 some account of the ideas on " complication " developed 

 by the latter. 



The second half of the first volume deals with crystal 

 structure and X-ray analysis and contains much new 

 matter. In particular, attention may be directed to the 

 well-illustrated and concise account of the Sohncke 

 point systems and also to the useful table of the 230 

 space groups, which will be found helpful as an intro- 

 duction to a somewhat inaccessible part of the subject. 

 Dr. Tutton's treatment arouses the wish that he had 

 used his powers of clear exposition to elucidate still 

 further these difficult but very important matters. 

 The chapter on the application of X-rays to the deter- 

 mination of crystal structure gives an admirable account 

 of the progress that has been made, while the sketch of 

 Fedorov's views on the correct setting of crystals and 

 on the compilation of a dictionary of crystal forms to 

 facilitate the identification of chemical compounds by 

 their morphology alone, whets our curiosity, and leads 

 us to wish that Dr. Tutton had shown us how to work 

 out the reticular density and the correct setting in a 

 few typical cases. 



The third section deals in the main with crystal 

 optics, and begins with an introductory chapter which 

 contains readable accounts of matters so diverse as 

 thermionic valves, radio-activity, atomic numbers, 

 isotopes, theories of atomic structure, the Zeeman 

 effect, Aston's positive ray mass spectrograph, the 

 Michelson echelon, and the Lummer-Gehrcke plate. 

 The succeeding chapters are in the main reprinted from 

 the first edition, but the treatment of the modes of 

 production of monochromatic light is fuller and includes 

 a useful description of the mercury vapour lamp. 

 When explaining the colour effects observed when thin 

 crystalline plates are placed between crossed Nicols, 

 ] >r. Tutton says : " The Nicol analyser itself introduces, 

 NO. 2757, VOL. I 10] 



when crossed to the polarising Nicol, a change of phase 

 of half a wave-length, like the act of reflection in the 

 case of thin films, and this A 2 requires to be added to the 

 retardation of one ray behind the other brought about 

 in traversing the crystal." Experience has shown that 

 this statement is a source of perplexity to the average 

 student, and it is to be regretted that Dr. Tutton has 

 not followed the more readily intelligible treatment 

 adopted by Groth in the successive editions of his 

 " Physikalische Krystallographie." 



The general excellence of the illustrations is so high 

 that the figures explanatory of the use of the mica 

 plate in finding the optical sign of crystals seem 

 scarcely to come up to the standard. A photograph 

 of the phenomenon reproduced as a plate would 

 have been more in keeping with the style of the 

 book. The figures and descriptions of polarimeters 

 for finding the optical rotation of liquids take up 

 valuable space and seem scarcely necessary in 

 a work on crystallography ; indeed, the connexion of 

 much of the matter in this section with crvstals is 

 somewhat remote, although the reader will perhaps 

 forgive the author its introduction for the sake of its 

 intrinsic interest, a case in point being the account of 

 the use of the barium platinocyanide screen for secret 

 signalling during the war. The last two chapters of 

 this section contain a full description of the various 

 types of microscopes and of the principal methods 

 employed in the microscopic examination of crystals, 

 both when isolated, or when occurring in rock slices. 



The concluding portion of the book opens with an 

 excellent discussion of isomorphism, isogonism, poly- 

 morphism, and enantiomorphism, which may be 

 especially commended to the notice of chemists, who 

 will find therein much interesting information as to 

 recent work not easily accessible elsewhere. The next 

 chapters are devoted to the thermal and elastic pro- 

 perties of crystals, and in particular to full descriptions 

 of the ingenious and elaborate apparatus devised by 

 Dr. Tutton for measuring them, and to these have been 

 appended somewhat irrelevant accounts of the Inter- 

 ferential Comparator for standards of length, the 

 Michelson Interferometer, and the Etalon of Fabrv and 

 Perot. The final chapters of the book are devoted to 

 the consideration of the electric and magnetic pro- 

 perties of crystals, and to a brief but sufficient account 

 of so-called " liquid crystals." 



It will be seen, then, that these tw r o volumes are a 

 mine of accurate information on matters belonging to 

 a wide field of knowledge, and testify alike to the learn- 

 ing and industry of the author and to the enterprise of 

 his publishers. The wealth of detail of many of the 

 descriptions, the large number and excellence of the 

 illustrations, and the considerable amount of irrelevant 



