PREFACE. THIS little volume, originally written in the spare hours of a long ocean voyage, deals with the means now used American cities to secure clean water. by Some closely allied subjects are also touched upon, including some matters of general policy, pressure, fire service, the sale of water, and the financial management of water works. This is because an understanding of these matters is often necessary to enable the means of securing a new supply, or improving an old one, to be fully considered. Matter descriptive of existing works and their man- can best agement is frequently used where principles be shown by it but it is the object to illustrate principles and not to describe the works that are mentioned. Its object is to help beginners to understand some- thing of the first principles. In the present edition chapters have been added upon the red-water trouble and upon the disinfection of water supplies, in the knowledge of which great advance has been made since the first edition. The statistics have also been brought up to the census of 1910, and corrections and additions made throughout the volume.