Publisher's Synopsis
From the Preface to the Third Edition.
The sale of 3000 copies of this book in little more than a year, many of them to persons of more education than I originally contemplated, has induced me to enlarge it considerably, going rather deeper into the subject, and adding some explanations which I did not venture on before. The additions chiefly relate to meteors, nebulae, and stars, the moon's acceleration and other disturbances, the tides, and the calculations for Easter in all ages; and a fuller account of the methods of weighing the sun, moon, and planets. The chapter on telescopes also has been greatly enlarged; for astronomy lives by them, and I do not know where a popular explanation of the theory of telescopes is to be found.
I keep to the plan of using as few 'diagrams, ' and as few words, as will serve the purpose, because I am satisfied that such explanations are both easier to read and to remember - provided of course they are explanations (see p. 100 n). A book is not a lecture. There it may be prudent to say things several times over, in different ways, and to illustrate them as well as you can; for the hearers must not stop to think, or they will be left behind. I have not scrupled to draw figures wherever I thought they would be useful. \ repeat the warning of the former editions, that this book only aims at making astronomy as easy as it can be made if difficulties and the reasons of things are really to be explained, and not evaded in vague language which leaves people as ignorant as before. It is idle to suppose that anything can be learnt of astronomy as a science of causes and effects, without some study and power of thought, and some natural capacity for geometrical conceptions. But those who cannot always follow the reasoning may still read the results, treating the book as one of 'descriptive astronomy' only, though it is really an introduction to 'physical astronomy, ' or the astronomy of causes and effects.
Though no mathematical knowledge is required of the reader, I do not profess anything so absurd as to rebuild the Newtonian system without mathematics. We soon come to a point in explanation where we must either stop and disclose no more, or else bridge over the chasm by adopting some simple result, or perhaps rather difficult calculation; such for instance as these two: that a sphere, but not a spheroid, attracts as if it were all condensed into its centre; and that the time of performing an elliptic orbit is the same as of the circle which contains it. All the arithmetical calculations here are founded on propositions as simple as these; and yet these require geometry, algebra, trigonometry, conic sections, and differential and integral calculus (or else other obsolete contrivances) to prove, though not to use them.
I have taken no small pains to avoid mistakes, but I cannot expect to have entirely succeeded; for even great astronomers occasionally commit them, from haste of writing or imperfect recollection; and sometimes they have to recant absolute mistakes of reasoning. I do not pretend to be an astronomer at all; but having been pressed into this service by a kind of accident, I have done the best I could for it.