rudimentary books for introducing beginners to the subject and for use in ordinary schools. But a good college text-book of geology has hitherto been wanting. There has been no American work for high-class institutions which treats the subject so as to meet the requirements of intelligent and scholarly people, who yet do not expect to become independent cultivators of geological science. This manifest gap has now been filled by the publication of the work before us, and a careful examination of the volume convinces us that it has been executed with great judgment with reference to the present needs of higher education. In his preface Prof. Le Conte thus states the purpose he had in view in writing the work: "I have attempted to realize what I conceive to be comprised in the word elements as contradistinguished from manual. I have attempted to give a really scientific presentation of all the departments of the wide field of geology, at the same time avoiding too great multiplication of detail. I have desired to make a work which shall be both interesting and profitable to the intelligent general reader, and at the same time a suitable text-book for the higher classes of our colleges. In the selection of material and mode of presentation, I have been guided by long experience as to what it is possible to make interesting to a class of young men, somewhat advanced in general culture and eager for knowledge, but not expecting to become special geologists. In a word, I have tried to give such knowledge as every thoroughly cultured man ought to have, and at the same time is a suitable foundation for the further prosecution of the subject to those who so desire. The work is the substance of a course of lectures to a senior class, organized, compacted, and disencumbered of too much detail by representation for many successive years, and now for the first time reduced to writing."
But, besides preparing a comprehensive text-book, suited to present demands, which was the author's main design, he has also given us a volume of great value as an exposition of the subject, thoroughly up to date. It is well known that geology is one of the most rapidly progressive of the sciences, but in recent years its advances have been very remarkable. Not only are its facts multiplying at an unprecedented rate, through the labors of the increasing multitude of geological observers in all lands, but its progress is to a still greater degree signalized by the light thrown upon it by various other sciences, and by the working out of fundamental principles by which its multitudinous details are organized into more perfect method. The law of evolution is now the key to geology. A vague principle of progress has long been obscurely recognized in geological phenomena, but that principle has now been brought out, amplified, formulated, and established, as the all interpreting law that has governed the unfolding of the globe. Much remains to be done, no doubt, in the elucidation of this grand principle, but its imperfection now becomes a measure of the imperfection of geology itself, and no presentation of that science is any longer possible which does not give prominence to the doctrine of evolution. Prof. Le Conte not only accepts it, but puts it to its proper scientific use, as his volume bears abundant witness, and as he explains in the following words from the preface: "In the historical part, I have found much more difficulty in being scientific without being tiresome, and in being interesting without being superficial and wordy. I have attempted to accomplish this difficult task by making evolution the central idea about which many of the facts are grouped. I have tried to keep this idea in view, as a thread running through the whole history, sometimes very slender—sometimes, indeed, invisible; but reappearing from time to time to give consistency and meaning to the history."
The examples and applications of Prof. Le Conte's work are almost entirely derived from this country, so that the treatise may be properly considered an American geology. This involves no narrowness or incompleteness; for, although science is as wide as Nature, yet the illustrations of geology are necessarily local, and an important point is gained when those are selected which will be most naturally observed by the great mass of students for whom the volume was designed. The region of the Rocky Mountains and the Western portions of the continent, as is well known, have
