Many of the illustrations which have been borrowed for use in this book are criticized adversely. It is the hope that all such criticisms will be accepted as an honest attempt toward an advance in the art of showing data in graphic form. In fairness to the authors of those charts which are criticized, it must be said that there has been a very rapid advance in the art of graphic presentation within the last few years and that many of these men would not present the material to-day by the methods which may have been used some years ago in the preparation of certain charts shown here. Where charts are used and criticized adversely, the charts have been included only because it is felt that they show a practice which is rather common but is nevertheless of questionable desirability. Many of the suggestions for standard practice contained in this book should be taken as tentative only. The American Society of Mechanical Engineers has invited about fifteen of the chief American societies of national scope to co-operate by sending one member each to a Joint Committee on Standards for Graphic Presentation. Though this committee is not yet completely organized, and it will be some time before any report is available, the reader who desires further information regarding standard practice should be on the lookout for any reports which the joint committee may publish in the future.