690. BOOK REVIEWS correctly and then identify and classify the rock. The book
may be divided into three parts. The two short introductory chapters describe ...
690
BOOK
correctly a n d t h e n identify a n d classify the rock. The book m a y be divided into three parts. The two short i n t r o d u c t o r y chapters describe v e r y briefly t h e collection a n d preparation of samples, the principles of mineral separation a n d the most i m p o r t a n t methods for further e x a m i n a t i o n of the sample. T h e n follows a good chapter dealing w i t h the microscopic e x a m i n a t i o n of minerals a n d aggregates, w i t h special emphasis on the determination of optical orientations. N e x t come a n e l e m e n t a r y account of the basic procedures for using the universal stage, a n d a little chapter on the graphical presentation of chemical d a t a for rocks, which includes the procedure a n d tables for the calculation of the C . - I . - P . - W . norm. The second p a r t (pp. 91-283) deals s y s t e m a t i c a l l y w i t h t h e optical properties of the rock-forming silicate a n d non-silicate minerals. The t r e a t m e n t here is excellent a n d again emphasizes the use of accurately determined optical properties for mineral recognition and, where possible, estimation of the chemical composition. The t e x t is supported b y numerous microphotographs of somewhat variable quality, easily read opticscomposition diagrams a n d good line drawings of imp o r t a n t habits of m a n y of the minerals, showing the orientation of the indicatrix. A v e r y useful set of determ i n a t i v e tables concludes this section. The final p a r t of the book is devoted to the recognition, description a n d classification of igneous, s e d i m e n t a r y a n d metamorphic rocks. The igneous a n d s e d i m e n t a r y chapters are clearly written a n d enable the rock to be classified b y combining optical mineral determinations w i t h structural a n d t e x t u r a l features. The final chapter, devoted to the classification of m e t a m o r p h i c rocks, is v e r y disappointing a n d is b y far the least satisfactory section of t h e whole book. I n adopting a structural approach, which of itself is quite useful, the a u t h o r has failed to m a k e a n y adequate reference to the chemical or mineralogical n a t u r e of the original rocks or to the conception of grade in m e t a m o r p h i s m . For its t r e a t m e n t of optic orientation, its presentation of the optical properties of minerals a n d its determinative tables the work can be highly recommended, b u t the early chapters, while providing a d e q u a t e references, are too brief to be really useful a n d the later chapters are no real substitute for a n adequate petrography. The book a t t e m p t s to cover too wide a field a n d at 62s. can h a r d l y be recommended to students for its optical mineralogy alone. I. I). MUIR
Department of Mineralogy and Petrology Cambridge, England
REVIEWS d y n a m i c s of crystal lattices to the engineering design of linear accelerators. This u n i t y arises from the presence, in each case, of identical systems coupled in succession, a n d shows itself m a t h e m a t i c a l l y in the necessity for using the same methods in solving t h e equations. Of course there are special problems relevant to each case, b u t there m u s t always be this basic isomorphism in t h e m a t h e m a t i c s to m a t c h the basic similarity in the physical structures. I t is n a t u r a l t h a t , w h e n a s t u d e n t is introduced to t h e t h e o r y of each particular problem, he should be t a u g h t b y specialists who only see their own aspect of it. I t is essential, before he plunges too deeply into the a d v a n c e d theory, t h a t he should read a book such as this to link all these specialized accounts together. The peculiar b e a u t y of the present m a t t e r is its great simplicity. There is no need of high-brow m a t h e m a t i c s . The emphasis is on the physical ideas, which are usually t h e simple m a t h e m a t i c a l i n v a r i a n t s of the equations. Pass bands a n d stop bands, impedance, group velocity, reciprocal space, zones, t r a n s f o r m a t i o n matrices, four-terminal networks, etc., are the concepts whose properties a n d uses are explained a n d developed. These are t h e abstractions in terms of which a n engineer or physicist m u s t learn to think. There is an enormous gain in seeing t h e m in their most general context, not merely as special devices in a restricted field of application. A b o u t two-thirds of the t e x t reads as a direct translation of the original work, w i t h a few minor additions, such as the rigorous proof t h a t the separate pieces of a single zone m a y be t r a n s l a t e d to exactly cover the first zone. The new material has been concentrated m a i n l y into four new chapters. Chapters 6 a n d 12 deal w i t h t h e work of M. Parodi in systematizing the solution of problems involving propagation in finite arrays. An elegant formalism, using the Gegenbauer polynomials, is introduced, a n d provides the s t a n d a r d solutions r a p i d l y a n d neatly. This looks useful, a n d should be better known. The two final chapters introduce essentially new topics - - p r o p a g a t i o n in slotted wave guides a n d the interaction of electrons w i t h m o v i n g periodic fields. The m a t h e m a t ical problems here are more complex, a n d only approximate solutions are offered. One has t h e feeling t h a t t h e m a t h e m a t i c a l a n d physical analogies w i t h t h e earlier, simpler cases m i g h t have been further exploited to m a k e the a r g u m e n t clearer. I n the hope t h a t a new English edition m a y ~oon appear, I offer the following criticisms in detail. The a r g u m e n t of § 47 is still as obscure in F r e n c h as it was in English, a n d seems merely to be a n a t t e m p t to fight again a n old battle a b o u t the self-consistency of t h e I)ebye theory of specific heats. The t r e a t m e n t of Bloch's theorem in two or three dimensions is superficial. No
Propagation des 0ndes dans les Milieux P~- mention or use is made of the gr0up-the0retical methods are fashionable n o w a d a y s in studies of crystal riodiques. By L]io~ BR~LLo~r~ and M_AURIC~ which structure. Something more m i g h t be said a b o u t systems PARODI. P p . 348 w i t h 185 figs. P a r i s : Masson. 1956. P r i c e 4,000 fr., b o u n d 4,600 fr.
Strictly speaking, this should be described as a new edition, m u c h enlarged, of Prof. Brillouin's book Wave Propagation in Periodic Structures, first published a b o u t t e n years ago in English. I n t h a t time it has become somet h i n g of a classic. The m a i n thesis, which it a d m i r a b l y presents, is t h a t there is a n underlying u n i t y in a great v a r i e t y of physical problems, ranging in scale from the
w i t h cyclic b o u n d a r y conditions, b o t h as a device to avoid surface effects in crystals, a n d in models of cyclic molecules (or, perhaps, of cyclotrons). B u t these are niggling points in a n a d m i r a b l y lucid account which could a n d should be read b y every p h y s icist or engineer before he burrows into his professional speciality. J . M . ZX~AN
Cavendish Laboratory Cambridge, England
