Produced by Tom Roch, Richard J. Shiffer and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images produced by Core Historical Literature in Agriculture (CHLA), Cornell University) [Transcriber's Note: Every effort has been made to replicate this text as faithfully as possible, including obsolete and variant spellings and other inconsistencies. Text that has been changed to correct an obvious error is noted at the end of this ebook. Also, on pages 47-48, the Greek letter theta is represented by THETA. In chemical and mathematical notations, a subscript is enclosed in braces and preceded by an underscore (e.g., H_{2}O.)] AGRICULTURAL ENGINEERING SERIES E. B. MCCORMICK, CONSULTING EDITOR FORMERLY DEAN OF ENGINEERING DIVISION KANSAS STATE AGRICULTURAL COLLEGE AMERICAN RURAL HIGHWAYS _McGraw-Hill Book Co. Inc._ PUBLISHERS OF BOOKS FOR Coal Age -- Electric Railway Journal Electrical World -- Engineering News-Record American Machinist -- Ingenieria Internacional Engineering & Mining Journal -- Power Chemical & Metallurgical Engineering Electrical Merchandising [Illustration: _Frontispiece_] AMERICAN RURAL HIGHWAYS BY T. R. AGG, C.E. PROFESSOR OF HIGHWAY ENGINEERING IOWA STATE COLLEGE FIRST EDITION MCGRAW-HILL BOOK COMPANY, INC. NEW YORK: 239 WEST 39TH STREET LONDON: 6 & 8 BOUVERIE ST., E. C. 4 1920 COPYRIGHT, 1920, BY THE McGRAW-HILL BOOK COMPANY, INC. PREFACE AMERICAN RURAL HIGHWAYS was written for use as a text or reference in courses dealing with rural highways and intended for agricultural engineers, students in agriculture and for short courses and extension courses. The reader is assumed to have familiarity with drawing and surveying, but the text is adapted primarily for students who do not receive training along the lines of the usual course in Highway or Civil Engineering. The text is intended to familiarize the student with the relation of highway improvement to national progress, to indicate the various problems of highway administration and to set forth the usual methods of design and construction for rural highways in sufficient detail to establish a clear understanding of the distinguishing characteristics and relative serviceability of each of the common types of roadway surface. Experience with classes made up of students in agriculture or agricultural engineering and with trade school students in road making served as a guide in the selection and arrangement of the material. Detailed discussion of tests of materials and of the theory of design has to a considerable extent been eliminated as being outside of the scope of the course for which the text is intended.