Alum Slate. 3 2 3 Obfervations. t. It bears a ftrong refemblance to bituminous ■frood, and probably paflfes into it. May it not be ' confidered as a fubfpecies of bituminous wood ? 2. We mull be careful not to confound it with alum ftone or alum flate, from which it differs very much. J . c - SIXTEENTH SPECIES. Alum Slate. Alaunfchiefer.—Werner. Werner divides this fpecies into two fubfpecies 1 • Common alum flate. 2. Glolfy alum flate. T t 2 FIRST