The Amateur Astronomer
Astronomy for Everyman. Edited by Martin Davidson. (Dent. 18s.; IN the preface it is claimed that this book provides an up-to-date and authoritative outline of our knowledge of the heavenly bodies. It is a composite work, eleven contributors having provided sections. There are consequently a great divergence in styles, some over lapping in contents and some conspicuous gaps. The great developments in the important branch of astronomy called astrophysics are scarcely mentioned ; there is nothing at all, for instance, about the internal constitution of the stars, stellar evolution or cosmology: The names of Eddington and Jeans do not appear in the index, though there is one brief reference to Eddington in the text. The index, incidentally, is singularly incomplete ; apart from the proper names (some of which have wrong initials and many have none), it seems to have been purely a matter of chance whether any particular subject is mentioned or not for subject references it is really valueless. The lack of balance of the book can be judged from the fact that seven chapters (285 pages) are devoted to the solar system, and only one chapter (72 pages) to the stars. With so limited an amount of space allotted to the stars, it is only the fringe of stellar astronomy that can be touched upon.
A shot t chapter on the history of astronomy is divided into two sections, the first dealing with the period from the earliest times to Flamsteed and the second with Flamsteed to modern times. The first section is good, and could well have formed an introductory chapter to the volume ; the second section is all too brief, is largely a catalogue, and inevitably overlaps the other chapters. It was doubtful wisdom to include chapters on navigation and interplanetary flight, which are not in unison with the other contents. Navigation is concerned with the determination of position on sea or in the air ; but there is no mention of the more general questions of determina- tion of time and'position, methods of surveying etc. The subject of interplanetary flight is speculative. Neither of these chapters is concerned with subjects that have contributed to our knowledge of the-heavenly bodies.
The book has a strong observational bias ; the chapters dealing with the bodies in the solar system are all by experienced observers and are the best and most useful. The chapter on instruments will be helpful to amateur observers, and the sections dealing with the sun, moon and planets will be much appreciated by amateurs who possess a small telescope, and particularly by those who have had little experience in observation. The reproductions of drawings of Mars emphasise the great diversity in the details of the same region of Mars as depicted by various observers, whereas photographs of Mars show only relatively minor changes. These drawings are in themselves sufficient to throw doubt on the reality of the narrow linear markings (popularly called canals) seen by some observers ; no two observers, in fact, seem to agree in the finer details of what they see. The difficulty of the observations must not be overlooked, however ; when the disc of Mars is at its nearest to the earth, a magnification of 72 is required to make it appear of the same angular diameter as the moon appears to the naked eye, and naked-eye observations of the moon can give very little information about the true nature of its surface.
Although this book has many defects, there is much in it that is of interest, particularly to the amateur observer. The star-maps of the northern and southern sky are unfortunately on much too small a scale to be of much use to the ordinary star-gazer.
H. SPENCER JONES.
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