I HAVE endeavoured in this book to give a simple description of the heavenly bodies and their motions in a form which should appeal to those who know little or nothing of the subject. It has been my aim to strike a mean between the larger and more difficult technical books and the extremely simple ones which weary us with accounts of children walking round tables and oranges. The book is the outcome of the notes which I have used in teaching Astronomy to Junior Forms in a Public School, where experience has shown me that many boys will follow up the subject, read for themselves, and enjoy practical work, when once they have been given a start.

THIS book is intended for the use of students who have a fair knowledge of elementary algebra and plane geometry, and is the outcome of several years of experience with classes of this sort. The author hopes that the volume will also be acceptable to more advanced scholars.

HPHE present volume is intended to meet the wants of those Students whose knowledge of Mathematics is limited to an acquaintance with the Elements of Euclid, Algebra, and Plane Trigonometry. In a few cases easy formulae in Dynamics are introduced, but the articles containing these may, if necessary, be omitted without a breach in the continuity of the work.

THE READER of this volume is expected to possess such knowledge of Mathematics as may be gained by studying the Elements of Euclid and Algebra, together with a rudimentary acquaintance with the geometry of Planes and Spheres.

I T must be in compliance with custom, rather than from any distinct view of good likely to result, when an Author begins his Work by defining the Science he means to treat of. A definition is not easily laid down. It is not difficult, indeed, to define a branch of science in general terms ; but such are seldom intelligible to the Student. If we enumerate what is too summarily expressed, and explain a general statement by detailing certain cases comprehended under it, we, probably, forestall what belongs to the body of the Work. We attempt to do immaturely what, it is almost certain, will be done imperfectly ; and this without an adequate advantage ; for, a definition such as we allude to, entailing no consequences, is not required in the beginning of a Work: at the end it is unnecessary.

EVERY one strives to adapt means to ends, and when the author prepared his large work on Astronomy, he had no other end in view than to teach Astronomy to such as may be competent to the task and fully prepared to learn it. His first aim was to produce a book of the right tone and character, without any regard to the number of persons who might be prepared to use it. That effort was entirely successful, but the book is not adapted to the great mass of pupils, because it requires of the learner considerable mathematical knowledge, and a corresponding discipline of mind, therefore but few persons, omparatively speaking, feel qualified to study that book. At the same time a book of like tone, character, and spirit, is demanded by teachers for the use of their more humble pupils, except that it must be on a lower mathematical plane, and this book is designed to supply that demand.

THE present volume is the first of a projected series having the double purpose of developing the elements of Practical and Theoretical Astronomy for the pecial student of the subject, and of serving as a handbook of convenient reference for the use of the working astronomer in applying methods and formulae. The plan of the series has been suggested by the author's experience as a teacher at the Johns Hopkins University, and as an investigator. The first has led him to the view that the wants of the student are best subserved by a quite elementary and condensed treatment of the subject, without any attempt to go far into details not admitting of immediate practical application. As an investigator he has frequently been impressed with the amount of time consumed in searching for the formulae and data, even of an elementary kind, which should be, in each case, best adapted to the work in hand.