PREFACE

In this little book I have attempted to give an account of the methods employed by astronomers and the reasons for some of the propositions they advance. Astronomical investigations frequently seem complicated owing to the amount of subsidiary detail, but the principles underlying them are simple and usually admit of a clear statement which can be followed by a general reader. In the introduction to his lectures delivered at Ipswich in 1848 Sir George Airy draws attention to an attitude towards Astronomy which is still prevalent. Such questions as the determination of the distance of the Sun or Moon are considered as beyond ordinary comprehension ; the instruments with which astronomical measurements are made are supposed to be based on obscure and difficult principles ; therefore the best a layman can do is to accept statements on the personal credit of the astronomer making them. He points out that this is an exaggerated view. The principles involved in measuring the distance of the Moon are no more abstruse than those employed to find the distance of a tree on the other side of a river. Astronomical instruments are as simple in principle and far less complicated in detail than a lathe or a steam-engine. It is quite true that in both instruments and methods many subsidiary details must be attended to when great accuracy is required in order that disturbing causes may be allowed for or eliminated. But an explanation of the essential principles may be given which can be readily understood with ordinary care and attention…

PREFACE

This volume is not a formal treatise on Astronomy, nor is it a mere educational text-book ; but the idea which underlies it may be realised from the following considerations. An extended experience as an astronomical writer, and likewise lecturer on the science, coupled with much intercommunication with many of its votaries in divers walks of life and places, including colonies and foreign countries, has led me to notice the remarkable spread of late years all over the world of a taste for Astronomy. Some recent eclipses of the Sun, and especially some recent comets, have had a good deal to do with this, especially Halley's Comet of 1910. I have often been struck by the frequent requests for information on astronomical topics from all sorts of people, the majority of whom, I fancy, would have resented a suggestion that they should sit down and seriously study text-books on the subject. These are the people whom I want to get hold of through this volume…

PREFACE

The reasons why a person with my sort of training should write this book are given in the body of it. For the control of matters there which lie outside my usual fields of study I am deeply obliged by help from several of my friends and colleagues, among them, and particularly, Floyd K. Richtmyer, Professor of Physics, who has been patient enough to read all the manuscript with critical attention. One way and another, I believe I have made effectual use of every one of his queries and comments, including those that touched upon the arrangement of certain of the earlier paragraphs. Helpful suggestions have come to me from other sources, too, and I hope the book is the better for my use of them. For any shortcomings that may remain no one is responsible but the author, who nevertheless is rejoiced to think that this work is the first book to be formally accepted by the Council of the Cornell University Press for publication.

PREFACE

From the time of its organization in 1889, the chief object of the Astronomical Society of the Pacific has been to stimulate interest in astronomy among the people of the Pacific region by giving to discoveries and advances made in that science the widest publicity through the medium of its Publications and, more directly, by means of public lectures. In harmony with this policy, plans were made early in the autumn of 1916 for a course of lectures to be given in San Francisco by members of the staff of the Lick Observatory, in the season of 1916-1917.

This textbook designed for advanced undergraduate students covers the foundations and principles in the field, and gives the necessary background for advanced courses. Beginning with a survey of some of the fundamentals of statistical mechanics, Collins builds up the physics of stellar structure step by step, showing where complexities arise due to the failure of assumptions.