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Geology is a science of such rapid growth that no apology isexpected when from time to time a new text-book is added to thosealready in the field. The present work, however, is the outcome ofthe need of a text-book of very simple outline, in which causesand their consequences should be knit together as closely aspossible,—a need long felt by the author in his teaching, andperhaps by other teachers also. The author has ventured,therefore, to depart from the common usage which subdividesgeology into a number of departments,—dynamical, structural,physiographic, and historical,—and to treat in immediateconnection with each geological process the land forms and therock structures which it has produced.
It is hoped that the facts of geology and the inferences drawnfrom them have been so presented as to afford an efficientdiscipline in inductive reasoning. Typical examples have been usedto introduce many topics, and it has been the author's aim to givedue proportion to both the wide generalizations of our science andto the concrete facts on which they rest.
There have been added a number of practical exercises such as theauthor has used for several years in the class room. These are notmade so numerous as to displace the problems which no doubt manyteachers prefer to have their pupils solve impromptu during therecitation, but may, it is hoped, suggest their use.
In historical geology a broad view is given of the development ofthe North American continent and the evolution of life upon theplanet. Only the leading types of plants and animals arementioned, and special attention is given to those which mark thelines of descent of forms now living.
By omitting much technical detail of a mineralogical andpaleontological nature, and by confining the field of view almostwholly to our own continent, space has been obtained to give towhat are deemed for beginners the essentials of the science afuller treatment than perhaps is common.
It is assumed that field work will be introduced with thecommencement of the study. The common rocks are therefore brieflydescribed in the opening chapters. The drift also receives earlymention, and teachers in the northern states who begin geology inthe fall may prefer to take up the chapter on the Pleistoceneimmediately after the chapter on glaciers.
Simple diagrams have been used freely, not only because they areoften clearer than any verbal statement, but also because theyreadily lend themselves to reproduction on the blackboard by thepupil. The text will suggest others which the pupil may invent. Itis hoped that the photographic views may also be used forexercises in the class room.
The generous aid of many friends is recognized with specialpleasure. To Professor W. M. Davis of Harvard University there isowing a large obligation for the broad conceptions and luminousstatements of geologic facts and principles with which he hasenriched the literature of our science, and for his stimulatinginfluence in education. It is hoped that both in subject-matterand in method the book itself makes evident this debt. But besidesa general obligation shared by geologists everywhere, and invarying degrees by perhaps all authors of recent American text-books in earth science, there is owing a debt direct and personal.The plan of the book, with its use of problems a