The combined researches of Anderson and Williams on the basic compounds contained in coal tar have led to the discovery of two well-defined series of organic bases, called respectively the Pyridine and Chinoline series, the members of both of which possess the properties of nitrile bases. The isomerism between the pyridine and the aniline series of bases excited considerable interest at the time of its discovery. The subsequent researches of Williams on the products of the distillation of chinchonine led to the discovery of bases having the same composition as the members of the pyridine and chinoline series of coal tar. When first discovered they were supposed to be identical. Since that time, however, a careful examination and comparison of the tar series of bases with the chinchonine series has led Mr Williams to the interesting discovery that the two lutidines, as also the two chinolines, are in reality not identical, but isomeric. This introduces a greater complexity into the study of the constitution of these compounds.