Experience in using the first list which we drew up of band heads arranged in order of wavelength showed that in extending this list to include a large number of molecules it was desirable to modify the system. The Tables for the Identification of Molecular Spectra are therefore divided into two sections. The first section consists of a list of the most prominent heads of the more persistent and better-known band systems of each molecule. These heads are listed in order of wavelength, with abbreviated information about the direction of degradation of the bands and their appearance, and, of...