Unfortunately, the chapters written by Messrs. Gilbert, Dutton, Thompson, and Drummond have not been proof-read by themselves, by reason of their absence during the time when the volume was going through the press; but this is the less to be regretted from the fact that the whole volume has been proof-read by Mr. J. C. Pilling, whose critical skill is all that could be desired. J. W. P. AUGUST, 1878. PREFACE TO THE SECOND EDITION The first edition of this report having been exhausted in a few months and without satisfying the demand which the importance of the subject created, a second was ordered by Congress in March, 1879. The authors were thus given an opportunity to revise their text and eliminate a few formal errors which had crept in by reason of their absence while the first edition was passing through the press. The substance of the report is unchanged. J. W. P. JULY, 1879. TABLE OF CONTENTS. CHAPTER I. PHYSICAL CHARACTERISTICS OF THE ARID REGION: Page. The Arid Region 5 Irrigable lands 6 Advantages of irrigation 10 Coöperative labor or capital necessary for the development of irrigation 11 The use of smaller streams sometimes interferes with the use of the larger 12 Increase of irrigable area by the storage of water 12 Timber lands 14 Agricultural and timber industries differentiated 18 Cultivation of timber 19 Pasturage lands 19 Pasturage farms need small tracts of irrigable land 21 The farm unit for pasturage lands 21 Regular division lines for pasturage farms not practicable 22 Farm residences should be grouped 22 Pasturage lands cannot be fenced 23 Recapitulation 23 Irrigable lands 23 Timber lands 23 Pasturage lands 24 CHAPTER II. THE LAND-SYSTEM NEEDED FOR THE ARID REGION: Irrigable lands 27 Timber lands 27