LIST OF ILLUSTRATIONS.facing pageInterior of covered pure-water reservoir at Washington, D. C.f before being filled with water. It is covered for the purpose of keeping the filtered water clean..........FrontispieceThe Old Croton Dam. This view was taken before the filling of the New Croton Dam, which now entirely submerges the old dam............................................ 2High Bridge in 1907. Built about 1840 to carry Croton wateracross the Harlem River to New York City............. 2The new Croton Dam holding back water for the supply ofNew York City...................................... 4One of the Boston Pumping Stations....................... 8Wachusett Dam of the Metropolitan Water Works for Bostonand Suburbs........................................ 8Tubercles Growing in Iron Water-pipes..................... 60An early type of Mechanical Filter at Chattanooga, Tenn..... 76The Little Falls Filters of the East Jersey Water CompaTable of Contents CONTENTS; Page; CHAPTER I; Impounding Reservoir Suppliesi; CHAPTER II; Water Supplies from Small Lakes 26; CHAPTER III Supplies from the Great Lakes 29; CHAPTER IV Water Suppliesfrom Rivers 32; CHAPTER V; Ground Water Supplies 42; CHAPTER VI; On the Action of Water on Iron Pipes and the; Effect thereof on the Quality of the Water 59; CHAPTER VII Development of Water Purification in America 67; CHAPTER VIII On the Nature of the Methods of Purifying Water 82; viii; CONTENTS; Pace; CHAPTER IX; On the Application of the Methods of Water Purification, Arranged According to the Mat-; ters to bk Removed by the Treatment 92; CHAPTER X; Storage of Filtered Water 114; CHAPTER XI; On the Required Sizils of Filters and Other; Parts of Water Works 116; CHAPTER XII; As to the Pressure under which Water is to be Delivered 123; CHAPTER XIII On t