Intro
This resource had its origin in the attempt to write an introductory work, dealing principally with American Geology, upon the lines of Sir Archibald Geikie’s excellent little “Class-Book.” In spite of vigorous efforts at compression, it has expanded to its present size, though the difference from the “Class-Book,” in this respect, lies not so much in the quantity of matter as in the larger size of the type and illustrations.
The resource is intended to serve as an introduction to the science of Geology, both for students who desire to pursue the subject exhaustively, and also for the much larger class of those who wish merely to obtain an outline of the methods and principal results of the science. To the future specialist it will be of advantage to go over the whole ground in an elementary course, so that he may appreciate the relative significance of the various parts, and their bearing upon one another. This accomplished, he may pursue his chosen branch much more intelligently than if he were to confine his attention exclusively to that branch from the beginning of his studies.
Students, and only too often their instructors, are apt to prefer a text-book upon which they can lean with implicit confidence, and which never leaves them in doubt upon any subject, but is always ready to pronounce a definite and final opinion. They dislike being called upon to weigh evidence and balance probabilities, and to suspend judgment when the testimony is insufficient to justify a decision. This is a habit of mind which -should be discouraged; for it deludes the learner into the belief that he knows the subject when he has only acquired some one’s opinions and dogmas, and renders further progress exceedingly difficult to him. In no science are there more open questions than in Geology, in none are changes of view more frequent, and in none, consequently, is it more important to emphasize the distinction between fact and inference, between observation and hypothesis. An open-minded hospitality for new facts is essential to intellectual advance.
The order in which the different sections of the book are taken up should depend somewhat upon the season of the year in which the study is begun. The chapter on the Rock-forming Minerals is intended rather for reference than for actual learning, and should at first be employed only to give the beginner a notion of what minerals are like and to familiarize him with a few of the commonest and most important kinds. The unfortunate likeness in the terminations of the names of so many minerals and rocks is a source of great confusion to the beginner. It is, therefore, important that he should have grasped the conception of what a mineral is, before commencing to deal with rocks. A repeated experience of this confusion has led to the wide separation of the chapter upon minerals from those treating of the rocks. It is perhaps hardly necessary to say that a knowledge of elementary inorganic Chemistry is indispensable to an understanding of almost any part of Geology, and especially of those parts which are concerned with the minerals and rocks.
If the course of study be commenced in the autumn, it will be well to take up first the chapters upon the Surface Agencies, or even the Structural Part, according to the opportunity for outdoor work and occasional excursions. When it is possible to undertake it, this work in the field should by no means be omitted. Even for those who have no intention of becoming geologists, observation at first hand possesses a far higher interest and charm and a much greater educational value than merely reading books or hearing lectures. Such observation is also a corrective of the false impressions which are necessarily given by the somewhat artificial and systematic treatment of a vast subject in a text-book. In many cases, it is impracticable for the teacher to take his class into the field. Under these circumstances he should constantly impress upon the minds of his pupils the inadequacy of all schemes and systems to embrace the great facts of nature, and should encourage them to observe for themselves, testing what they read by what they see.
In preparing this book, I have of course availed myself of material wherever it was to be found, but I wish to acknowledge my special obligations to the text-books of Dana, Le Conte, Geikie, Green, Prestwich, Credner, Kayser, Neumayr, Koken, de Lapparent, and Jukes-Brown. From the last-named writer is taken the arrangement of the Dynamical Agencies, which experience in the class-room has led me to consider as the best. Besides these general works, I have received great help from monographs and special articles by many writers, particularly from those by Clark, Cross, Dale, Dean, W. M. Davis, Gilbert, Harris, Kemp, Russell, Van Hise, Walcott, Willis, Weed, and others.
I take sincere pleasure in acknowledging the extremely kind and ready assistance which many fellow-workers in all parts of the country have granted me with unsparing liberality. Mr. Walcott, Director of the United States Geological Survey, has been especially kind in this respect, and has allowed the fullest use of the Survey’s fine collection of photographs. The liberal way in which advantage has been taken of this permission is to be seen in the many illustrations in the following pages marked (U. S. G. S.), all of which were made from the Survey photographs. Many other members of the United States Geological Survey have spared no pains to help me in the work of compilation, with advice, information, papers, drawings, photographs, and every other means in their power. To these gentlemen my obligations are very great, and to Messrs. Walcott, Cross, Emmons, Gilbert, Hill, ‘Weed, and Willis I wish to express my cordial thanks for many acts of kindly and most valuable assistance.
Professor J. F. Kemp was so kind as to send me the advance sheets of his” Lecture Notes on Rocks,” of which extensive use has been made. Mr. A. Smith Woodward, Mr. Agassiz, Dr. Bashford Dean, and Professor 1. C. Russell have kindly supplied me with illustrations from their books. Mr. Lucas of the U. S. National Museum, Dr. C. Hart Merriam of the U. S. Agricultural Department, Professor R. D. Salisbury, Professor Calvin of the Iowa Geological Survey, Mr. Pynchon of Hartford, and the officers of the Pennsylvania Railroad Company have furnished many valuable photographs. My colleagues, Professors Magie and Libbey, have assisted me with the proofs, and the latter has allowed the free use of his collection of unpublished photographs taken in Greenland, Alaska, and the Hawaiian Islands. Another colleague, Dr. A. E. Ortmann, has taken great pains in the selection of figures of the American fossil invertebrates, which have been redrawn by Mr. R. Weber, University Draughtsman. My friend, Dr. Baur, has been my guide through the tangled mazes of the synonymy of the American fossil reptiles. To these gentlemen, one and all, hearty gratitude is due for oft-repeated and unstinted kindness.
No one can be more conscious than the author of the very imperfect character of his performance, but he ventures to hope, nevertheless, that the book may find a place of usefulness, supplementary to the host of excellent works on Geology already in existence.