tus proceeds in a systematic way to develop the subject under discussion, proceeding regularly from the general to the particular, foreshadowing what is to come and making easy transitions from one phase of the general subject to another. Though his whole method of treatment is logical enough, the classification or system resulting from it, being grounded upon superficial appearance and behavior rather than upon any concept of chemical composition, necessarily has marked limitations. Nevertheless, from a scientific standpoint this little treatise is much better than the other ancient and medieval works on minerals that are known to us. Pliny, for example, though he treats the subject far more extensively, does so in a much less critical and systematic fashion. The comparative freedom of the treatise On Stones from fable and magic should be especially noted, for many of the works in this field written centuries later, particularly the medieval lapidaries, dwell largely upon the fancied magical or curative powers of precious stones. In fact, for almost two thousand years this treatise by Theophrastus remained the most rational and systematic attempt at a study of mineral substances.
