WHEN the Syndics of the Cambridge University Press did me the honour of offering to publish a collection of my mathematical papers, I had to consider the method of arrangement which would be most convenient. A simple chronological order has been adopted in various collections of this kind, and this plan certainly has advantages; but an arrangement of papers according to subject may be more convenient. In the case of my own work the separation into well-defined groups of subjects was easy, and I have therefore adopted this latter method. I shall, however, give at the beginning of each volume a chronological list with a statement as to the volume in which each paper will be found.

This first volume contains papers on Oceanic Tides and on an attempt to measure the Lunar Disturbance of Gravity; the second will give my papers on Tidal Friction and on the astronomical speculations arising therefrom; the third will be devoted to papers on Figures of Equilibrium of Rotating Liquid and on cognate subjects; and the fourth will be on Periodic Orbits and on various miscellaneous subjects.

Throughout corrections and additions will be marked by inclusion in square parentheses.

The whole of my work on oceanic tides and the attempt made by my brother Horace and me to measure the attraction of the moon sprang from ideas initiated by Lord Kelvin, and I should wish to regard this present volume as being, in a special sense, a tribute to him.