ΤΟ THE REV. W. RUTTER DAWES, F. R. A. S. &c. &c. &c. MY DEAR MR. DAWES, In availing myself of your permission to dedicate to you an Edition of these Outlines, enriched by accounts of several of your own recent discoveries, I should ill acquit myself to my own feelings if I did not add to the expression of that grateful sense of your many and important services to our common Science, which every astronomer must acknowledge, that of affectionate esteem and regard, the natural result of a prolonged and most friendly intercourse. Believe me, Very truly yours, Collingwood, Feb. 15. 1858. J. F. W. HERSCHEL. PREFACE ΤΟ THE FIRST EDITION. THE work here offered to the Public is based upon and may be considered as an extension, and, it is hoped, an improvement of a treatise on the same subject, forming Part 43. of the Cabinet Cyclopædia, published in the year 1833. Its object and general character are sufficiently stated in the introductory chapter of that volume, here reprinted with little alteration; but an opportunity having been afforded me by the Proprietors, preparatory to its re-appearance in a form of more pretension, I have gladly availed myself of it, not only to correct some errors which, to my regret, subsisted in the former volume, but to remodel it altogether (though in complete accordance with its original design as a work of explanation); to introduce much new matter in the earlier portions of it; to re-write, upon a far more matured and comprehensive plan, the part relating to the lunar and planetary perturbations, and to bring the subjects of sidereal and nebular astronomy to the level of the present state of our knowledge in those departments. The chief novelty in the volume, as it now stands, will be found in the manner in which the subject of Perturbations is treated. It is not-it cannot be made elementary, in the sense in which that word is understood in these days of light reading. The chapters devoted to it must, therefore, be considered as addressed to a class of readers in possession of somewhat more mathematical knowledge than those who will find the rest of the work readily and easily accessible; to readers desirous of preparing themselves, by the possession of a sort of carte du pays, for a campaign in the most difficult, but at the same time the most attractive and the most remunerative of all the applications of modern geometry. More especially they may be considered as addressed to students in that university, where the "Principia" of Newton is not, nor ever will be, put aside as an obsolete book, behind the age; and where the grand though rude outlines of the lunar theory, as delivered in the eleventh section of that immortal work, are studied less for the sake of the theory itself, than for the spirit of far-reaching thought, superior to and disencumbered of technical aids, which distinguishes that beyond any other production of the human intellect. In delivering a rational as distinguished from a technical exposition of this subject, however, the course pursued by Newton in the section of the "Principia" alluded to, has by no means been servilely |