REVIEWS 31 1

The first two chapters deal with the general aspects of computation. The use of desk machines is described at length, as is the organization of a calculation and the arrangement of work. Much useful information about unavoidable errors and the degree of accuracy of a computation can also be found here, as well as some comments about the ways in which random mistakes occur, how they can be detected, and how they can be put right.

The next two chapters on the evaluation of formulae and the use of finite differences are very well written with some useful worked examples, but these will be of only slight interest to the meteorologist. Random mistakes are introduced into the calculations and the way in which they can be found and corrected is very enlightening.

The chapter on ordinary differential equations shows how numerical solutions to various types of these equations can be obtained. One-point and two-point boundary conditions are discussed. The methods described in detail are the step-by-step processes through a series of equal intervals of the independent variable, Richardson’s deferred approach to the limit, and various iterative processes.

The chapter on partial differential equations is of great interest to the meteorologist engaged in research into the use of numerical methods in weather prediction, for quite a large part of this chapter is devoted to methods of solving the Laplace, Poisson and Helmholtz types of equations, which are equations which occur frequently in dynamical meteorology. The relaxation method is the most suitable for hand computation and is discussed at length but there is also a short section dealing with the Richardson - Liebmann process which is more suitable than relaxation methods for use on electronic computing machines.

The final chapter of the book gives an introduction to the problem of organizing a calculation for EDSAC, the electronic computing machine a t the Cambridge mathematical laboratory. It is written in non-technical language and is very easy to follow. Two elementary examples of arranging a set of instructions which whould enable the machine to carry out a simple calculation are given.

The book also deals quite adequately with methods of solving non-linear algebraic equations, inter- polation, quadrature and differentiation, and these methods may from time to time be needed by meteorolo- gists.

The book is written very well indeed and is easy to read. There is little literature on the subject to compare it with, but it is outstanding because it emphasizes the practical problems of computation. The aim of the book is to provide practical information about what calculation to make to obtain the required result, and how to make it. It does this, and is thoroughly recommended.

F.H.B.

Propagation of Short Radio Waves. Vol. 13, M.I .T . Radiation Laboratory Series. Edited by D. E. Kerr. New York (McGraw-Hill), 1951. Pp. xvii, 728; 299 Figs., 47 tables. 85s.

London (Hollis and Carter), 1952. The use of radar at sea. Edited by Capt. F. J. Wylie, R.N. Pp. xv, 279; 170 Figs., 9 tables. 30s.

A considerable amount of research on the propagation of short radio waves was carried out during the second world war. Many of the results of this research have been published in the form of reports with only a limited circulation. The purpose of the first of these two books is to summarize the state of knowledge, regarding propagation in the wave band from about 3 m to 1 mm, at the end of the war, though footnotes indicate that reports as recent as 1950 have been considered. It is written by members of the Propagation Group of the Laboratory as an interim report for research workers and covers work done in America, England, Canada and other Dominions. Although not a text-book each chapter gives sufficient of the basic background of its subject for an appreciation of the work described.

After a brief introductory chapter, the second chapter of about 150 pages deals with the theory of propagation in a horizontally-stratified atmosphere, including the computation of field strength with a linear modified-refractive-index profile. Chap. 3 considers in some detail the meteorological parameters which govern the profile of refractive index up to about 2,OOOft and includes a discussion of the effect of eddy diffusion and of heating and cooling from below with numerous empirical results. The fourth chapter summarizes the principal experiments on the investigation of the effects of atmospheric refraction on micro- wave transmission. Chap. 5 deals with the effects of reflection of radio waves from the earth‘s surface. A long Chap. 6 discusses the radar cross-section of a number of targets, sea echo, echo fluctuations and clutter echoes. The seventh chapter is devoted to meteorological echoes and includes both theoretical work and a number of photographs of typical P.P.I. displays. Finally the last chapter gives a theoretical and empirical treatment of attenuation owing to absorption by gases, water vapour, liquid-and solid-precipitation particles. Although the preface disclaims any attempt to deal with the forecasting of radio and radar-propagation performance or with climatological studies there is no doubt the meteorological forecaster who has to deal with such matters would find some assistance, particularly in Chaps. 3 and 7. For the research worker the book can be thoroughly recommended. The production, of course, is up to the usual McGraw-Hill standard.

The second of these two books is also a joint work by a number of authors but is written for a very different reader. It is produced by the Institute of Navigation with the declared aim ‘to give the mariner a complete and practical guide to the applications of marine radar and to the many factors which affect the results obtainable.’ The first three chapters deal with the general principles of radar and the equipment, and the next four with the propagation of waves, radar meteorology, interpretation of echoes and unwanted

312 REVIEWS

echoes. There follow four chapters related to radar as a navigational aid and six chapters dealing with miscellaneous matters, including maintenance. The treatment throughout is simple and involves no mathe- matics. The text is plentifully illustrated with diagrams and the photographs of radar displays are good. Only the mariner can decide whether the book achieves its aim and the reviewer claims no special knowledge of the sailors’ problems. Nevertheless it is apparent that the contributors to the book are practical men with appreciation of marine problems.

A.C.B.

The tropical rain forest. By P. W. Richards. Cambridge University Press, 1952. Pp. xviii, 450; 43 Figs., 15 plates, 39 tables. 63s.

The tropics cover nearly five times the area of the arctic and antarctic regions combined; they support a vast population, and contain almost limitless natural resources. An extension of our knowledge of tropical regions is of first importance, but botanists, no less than meteorologists, have hitherto been inclined to neglect the tropics in favour of temperate regions. Prof. Richards’s book is a detailed study of the ecology of tropical rain forests, well written, well produced, and very fully documented. The line drawings are excellent; the photographs good considering the grey twilight which prevails within the forest.

The author treats the forest as a plant community, whose members are influenced by one another and by environmental factors such as climate, topography and soil. Little is said, on the other hand, about the influence of the forest on its environment, the animal life which inhabits it, or its economic value to man. For this reason the book will be of value mainly to botanists and foresters, while the zoologists, geographers and others, to whom also the author addresses his work, will find it somewhat heavy going, particularly as no glossary of botanical terms is included.

Meteorologists will be interested in the section dealing with environment, which includes a masterly discussion of the available information regarding the climate of the rain forest regions and the microclimate within the forest. The climatic requirements are a high and very even temperature, and heavy rainfall spread over the greater part of the year; typical rain forests are not found where there is a prolonged seasonal drought. The areas covered by tropical rain forests (which, incidentally, account for about half the forested areas of the world) are irregularly distributed, here and there extending beyond the tropics, and in other places to only a few degrees north or south of the equator. This irregularity is attributed mainly to the uneven distribution of land and sea and its effect on rainfall. In tropical Australia, for instance, the rain forest in confined to a strip along the Queensland coast which is exposed to the S.E. Trades.

The author uses saturation deficit as an index of atmospheric humidity, for this gives a measure of the evaporating power of the air. In the interior of the rain forest the air remains nearly saturated throughout the twenty-four hours, particularly in the wet season, and it is remarkable that many of the lesser plants and trees within the forest show such rapid growth where the rate of transpiration must be slow, and the light is poor.

Owing to erosion and leaching by heavy rains, the soil in open situations in the tropics is often poor. Once the rain forest has become established, however, it protects the soil; the plant nutrients are locked up in the living vegetation and in the humus layer, and luxuriant growth is possible. Man, when he clears the forest, destroys this protection ; after a very few years of cultivation the soil becomes impoverished, the site is abandoned, and a fresh clearing is made. This wasteful system of shifting cultivation is practised by the natives in all rain forest regions.

The author deplores the rapid destruction of tropical rain forest by man. W e agree that the timber resources of the forest could be more effectively utilized, and the cleared land more economically cultivated, As the author suggests, large areas of virgin forests in different parts of the tropics should be conserved on account of their botanical and scientific interest. Personally we do not agree that the rain forest has much aesthetic value. There is little beauty in those tall unbranched trunks rising to a dense canopy of dull green above, the tangle of tlimbers and ‘ stranglers ’ beneath, the uniformity of the leaves, and the absence of seasonal changes. What can compare with a beech tree in spring or a glade carpeted with bluebells and primroses ?

The world is running short of food, and will soon run short of fuel. Tropical lands, where sunshine and rainfall are bountiful, can surely be made to produce more food, if the problems of soil conservation can be solved. And perhaps, as Hoyle suggests, our future supply of energy will not be from atomic sources, but through the capture of solar radiation by suitable tropical vegetation, which can be made to yield fuel alcohol. ‘ The jungle is neutral ’ ; maybe it can be replaced by plant life which is beneficial to mankind.

G.S.P.H.

Bulletin de I’Observatoire du Puy de Ddme (Quarterly). 2nd Series, No. 1 ; Jan. 1953. University of Clermont-

Geofisica e Meteorologia. Vol. I, No. 1, 1953. Bulletin of the Italian Society for Geophysics and Meteorology; Genoa. Pp. (12in. X Sin.) 28; Figs. N.p.

W e welcome warmly the reappearance, after a lapse of some years and in a slightly modified form, of the Bulletin of the Puy de Ddme Observatory. Its editor is H. Dessens; its aim, stated on the cover, to act

Ferrand. Pp. (94in. X 6in.) 32; Figs. 100 fr.