Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. A great deal will be found in these pages that will be of practical service, particularly to those who have not been able to read the works of Chevreul, Von Bezold, Rood, Church, and others. Indeed, even in these, careful study would be nec essary to select passages describing combinations that could be applied to special work.