PREFACE.

VII

upon the surfaces of the various planets to the constitution oftheir gaseous envelopes.

In the preparation of the Lectures most existing manualsand popular works upon Astronomy were freely employed, hutthe references were not in every case retained, as they werenot needed for viva voce use. The author has, however, en-deavoured to record his indebtedness wherever it was possible.Any omission to do so is quite unintentional.

He begs to state that he owes much to Mr. Proctor’s works,especially to those upon the Moon and Saturn; to variousvolumes and articles by Mr. Lockyer; to Mr. G-. F. Chambers’“Handbook of Descriptive Astronomy;” to many pages of theObservatory ; to Sir G. B. Airy ’s “Ipswich Lectures;” to Pro-fessor Hewcomb’s “Popular Astronomy ;” to Grant’s “Historyof Physical Astronomy ; ” to Sir ^L^Herschel’s “ Outlines ofAstronomy;” to Professor Young’s “Treatise upon the Sun;”to Dr. Ball’s “ Elements of Astronomy ; ” to the “ Annuaire ofthe Bureau cles Longitudes,” and to that of the Royal Obser­ vatory of Brussels ; to Sir E. Beckett’s “ Astronomy withoutMathematics;” and to the Rev. T. W. Webb ’s “CelestialObjects for Common Telescopes.”

He tenders his thanks, for much kind advice and informa-tion, to the Astronomer Royal; to Dr. Huggins, for veryvaluable assistance, particularly in connection with Lecture II.;to Dr. Hind, Superintendent of the Hautical Almanac ; to Mr.Dale, Fellow of Trinity College, Cambridge ; to Mr. Bentley,who has allowed two diagrams to be copied from the English edition of Guillemin’s “The Heavens”; to M. Niesten, forpermission to reproduce a drawing of the orbits and distri-bution of the Minor Planets; to Mr. N. Green, for his mostliberal loan of the lithographic stone of his chart of Mars ;to the Council of the Royal Astronomical Society , for thepicture of the Sun’s Corona in Plate IV., and for theviews of Jupiter in Plate VIII.; to Mr. G. D. Hirst, who