An attempt has been made in these pages to trace the evolution of intellectual thought in the progress of astronomical discovery, and,by recognising the different points of view of the different ages, to give due credit even to the ancients. No one can expect, in a history of astronomy of limited size, to find a treatise on "practical" or on "theoretical astronomy," nor a complete "descriptive astronomy," and still less a book on "speculative astronomy." Something of each of these is essential, however, for tracing the progress of thought and knowledge which it is the object of this History to describe...

THE chief authority for the Life of Sir William Herschel is Mrs. John Herschel's " Memoir of Caroline Herschel " (London, 1876). It embodies Caroline's Journals and Recollections, the accuracy of which is above suspicion. William himself, indeed, referred to her for dates connected with his early life. The collateral sources of information are few and meagre ; they yield mere gleanings, yet gleanings worth collecting. Professor E. S. Holden has had recourse to many of them for his excellent little monograph entitled "Herschel, his Life and Works" (London, 1881), which is usefully supplemented by "A Synopsis of the Scientific Writings of Sir William Herschel," prepared by the same author with the aid of Professor Hastings...

FOR a full explanation of the circumstances in virtue of which the matter forming the contents of this volume now appears dissociated from that to which it was joined in the first three editions of this work the reader is referred to Vol. I. of the 4th edition, published in September, 1889. Suffice it therefore now to state briefly what has been done to render the contents of this volume as acceptable as possible to the public.

PT^HE remarks which appear in the Preface to the Third Edition (see post] apply almost word for word, so far as they go, to the Fourth Edition. Yet it is necessary for me to write an independent Preface in order to call attention to the altered circumstances under which this work is now presented to the reader. If the development of Astronomy between 1867 and 1877 was great, its development between 1877 and 1889 has been still greater. And besides this, there were important omissions in the ground-plan of the book which I have long been very desirous of making good, whenever time or opportunity became available.

THERE is bat little alteration in this edition, for so far as regards the older astronomers at all events there has been nothing to add or to correct. It may, however, be mentioned here that a commemorative tablet has recently been placed on the house, in New King Street, Bath, in which William Herschel resided. Nor could it be possible to allow the sketch of the late Earl of Eosse to be reprinted without adding the fact that his youngest son, Hon. C. A. Parsons, is, as all the world knows, the famous engineer who invented the steam turbine.

THE rapid progress of the science of astronomy, for the liwr. "few years, has again rendered it necessary to revise the Geography of the Heavens a work, the popularity of which is sufficiently proved by a sale of 300,000 copies. The editor has, therefore, availed himself of the occasion to make such improvements, both in the book and maps, as seemed to be demanded by the progress of the science, and the most approved methods of instruction.

In this work the Author has endeavoured to cover as wide a field as possible and it has necessarily been somewhat difficult to decide upon what to include and what to omit, especially when dealing with the most recent developments. It is hoped, however, that the book will serve to give the reader a sufficiently complete view of the present state of Astronomy.

DURING the past few years great advances have been made in astronomical science. A new horizontal parallax of the sun has been established. This has materially altered the estimated distances, etc., of the planets. The sun is much nearer us than we supposed, and light has lost a little of its wonderful velocity. , Much additional information has been obtained concerning Meteors and Shooting Stars. The investigations connected with Spectrum Analysis have been especially suggestive.