The papers republished in this volume have appeared in various Magazines, Contemporary Review, Exposi tor, journal of the Royal Asiatic Society, Geographical journal, to the editors of which my thanks are ten dered. Most of them have been profoundly modified and much enlarged; but only in the last, which is made up of six older articles, is there any essential change in the original opinions. Elsewhere, the alterations which have been introduced are intended to render more precise and emphatic the views formerly stated. Even the first article, which has been little changed in expression, has been greatly enlarged. Only in the sixth article (first published in 1882) have the additions been indicated.