Chapter I: Preface

The object of the present work is not so much to instruct as to suggest. It represents a sort of reconnaissance, and embodies the information collected by scouts and skirmishers regarding practicable lines of advance and accessible points of attack, with a view to annexing for the realm of knowledge some further strips and corners from the territory of ignorance. Its inspiring motive, in short, is the desire for a rectification of the frontier in the interests of science. Material resources for the furtherance of such encroachments are not lacking. The globe is studded with observatories, variously and admirably equipped. Yet innumerable objects in the sidereal heavens remain neglected, mainly through inadvertence to the extraordinary interest of the questions pending with respect to them. In the following pages it has been sought to indicate some of these individually, and in their relations to the larger meanings of cosmical research. But this could be done effectually only from the vantage-ground of our actual acquirements; hence the book, although primarily designed to stimulate the progress of astrophysics, necessarily includes an account of its present state. Before attempting to add to our store of learning, we must realise what is already possessed.

The unknown, it is true, is indefinitely vast, and the rays of light which we can project into its darkness penetrate but a short way. Our programme of inquiry must accordingly be limited to what is now practicable, or promises to become so in the immediate future. The unforeseen, too, will have something, perhaps much, to do with prescribing directions for fresh researches. Queries, in the coming years, will be put to the skies very different from those here propounded; and answers of a surprising kind will doubtless be afforded to our present interrogatory. The keen delight of such revelations will reward those who, loving truth for its own sake, have laboured for its promotion; and if these pages should, in any degree, help to quicken and guide their noble enthusiasm, they will have amply served their purpose.

They do not, however, cover the whole field of astrophysics. Planetary and cometary astronomy are deliberately, although for different reasons, excluded from treatment in them. The moon and planets still belong to the theoretical and descriptive departments of the elder celestial science. Nearly all that is known about their condition has been learned by direct telescopic observation. The items of information added through the aid of the camera and the spectroscope, though valuable, are very few. The orbital characteristics, on the other hand, of comets and meteors are too prominent to be set aside in any profitable discussion of their nature. They are of the very essence of the phenomena; yet they would be out of place in a book strictly limited to the consideration of the heavenly bodies under their physical aspect.

The writer has received much courteous help from various quarters in preparing the illustrations, and desires in particular to acknowledge her obligations to Sir William and Lady Huggins, to Sir David Gill, to Dr. Roberts, F.R.S., to the Rev. W. Sidgreaves, S.J., Mr. W. E. Wilson, F.R.S., M. Deslandres, Professor Hale, Professor Barnard, to Professors E. C. and W. H. Pickering, and to Professor Campbell.

LONDON, _December 1902_.

CONTENTS

INTRODUCTION
PAGE
RISE AND SCOPE OF ASTROPHYSICS 1