Book Reviews

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brief descriptions of the different kinds of lasers known (but the Snark-like X-ray laser isnot mentioned) and another on properties of laser light ; this latter is chiefly a formulationof coherence theory applied to lasers, with a brief mention of speckle . Finally there arechapters on applications (too brief to be of any use) and on some recent advances ; thislast is mainly an expansion of earlier topics in terms of the semi-classical theory . Thereare useful examples and good sets of references for each chapter .

I can recommend the book as a good introduction to the subject for anyone who isinterested in the physical principles . The translation is clear and idiomatic . There isonly one criticism to be made and that applies to all books on lasers I have read, that noattempt is made to explain the spectroscopic notation used ; this is often confusing to thenon-specialist, when, e.g., in a diagram for ruby a pair of energy levels is labelled 2E and theupper and lower levels of this pair are respectively 2A and E ; an appendix giving theessentials might be useful . However, it does not really matter most of the time since thenon-spectroscopist can regard the notation simply as an irrational labelling system .

W. T. WELFORD

Einfiihrung in die Farbmetrik . By MANFRED RICHTER . (Berlin and New York : Walter deGruyter, 1976 .) [Pp. 276 .] Price DM 19 .80 .

MOST of this book is devoted to a clear and precise exposition of the nature of colour measure-ment, of the bases from which it starts and of the boundaries within which one can speakof true measurement . This is aided by a description of ocular structure and functionand by a number of suggested experiments and demonstrations. The mathematics ofthe subject is carefully dealt with throughout, which is one of the most helpful features ofthe book .

Now the book is called an introduction and it certainly starts at the beginning andtakes the reader meticulously into the heart of the subject. It is possible, however, thatthe complete beginner may find the book difficult reading and should have another book,such as Wright's ' Measurement of Colour ', for parallel study . Another aspect of theword ' introduction ' is that it takes the reader into the subject and then leaves him inthe middle: he should bear in mind that in this or that direction, perhaps in every direction,there is further knowledge to be gained, further progress to be made . The author mentionsthis occasionally, though not always .

Excellent though this book is, it is not without defects . The few misprints are suffi-ciently obvious not to be troublesome. The German script capitals, of which considerableuse is made throughout the book to denote primary colour valence, could be of a betterfount which differentiates more clearly between B and V ; in a few places very close scrutinyis needed to distinguish which is being used . The most tiresome defect, however, is thelack of chapter numbers in addition to chapter titles on the page headings . The authormakes frequent reference to other chapters, both fore and aft of the one being read,and this defect notably slows down the process of finding the desired bit .

The format of the book is one of its good features, fitting as it does into the side pocketof jacket or lab-coat for instant reference . Thinking of the reference aspect of the book'susefulness, it is a little disappointing that many convenient tables are not included . Thisis intentional, however : the author tells the reader to work out for himself any special tableshe may need! The essential basic tables for this are, indeed, in the book .

A final word may be added about bibliography and references : these are adequatefor the size of the book, but with, perhaps, a slight bias towards those in the Germanlanguage .

B. H. CRAWFORD

Nonemissive Electro-optic Displays . Edited by A . R . KMETz and F . K. VON WILLISEN .(New York : Plenum Press, 1976 .) [Pp. xix+360 .] Price US $42 .00 .

THIS book contains a collection of papers on non-emissive electro-optic displays and isthe proceedings of a symposium held in September 1975 at the Brown Boveri ResearchCentre, Baden, Switzerland . These cover the entire range of known, non-emissive,electro-optic display effects and are written by acknowledged experts in the various fields .The book is a valuable addition to the literature of such displays since the various papers