This is the third edition of a standard work which, though small in size, covers its subject to such an extent that it is perhaps as often quoted as any. The author's remarks are throughout judicious and his ideas as to the importance of the study of the source of water supply as well as the using of chemical and bacteriologic examinations are such as ought to be pretty thoroughly impressed upon those who have to do with this subject. The legal portion of the work has been revised and may be presumed to be thoroughly up to the most recent English laws. He has also added a chapter on the protection of water supplies. The book is one that will maintain its position as one of the leading works on its subject.