The last or sixth edition of my Elements of Geology was already out of print before the end 'of 1868, in which year I brought out the tenth edition of my Principles of Geology. In writing the last-mentioned work I had been called upon to pass in review almost all the leading points of specula tion and controversy to which the rapid advance of the sci ence had given rise, and when I proposed to bring out a new edition of the Elements I was strongly urged by my friends not to repeat these theoretical discussions, but to confine myself in the new treatise to those parts of the Ele ments which were most indispensable to a beginner. This was to revert, to a certain extent, to the original plan of the first edition; but I found, after omitting a great number of subjects, that the necessity of bringing up to the day those which remained, and adverting, however brie?y, to new dis coveries, made it most difficult to confine the proposed abridgment within moderate limits. Some chapters had to be entirely recast, some additional illustrations to be intro duced, and figures of some organic remains to be replaced by new ones from specimens more perfect than those which had been at my command on former occasions. By these changes the work assumed a form so different from the sixth edition of the Elements, that I resolved to give it a new title and call it the Student's Elements of Geology. In executing this task I have found it very difficult to meet the requirements of those who' are entirely ignorant of the science. It is only the adept who has already overcomexiv preface.