COMMENTARY. There can be no doubt that it was Pumice. Pumice, according to the latest analysis, is found to contain silica, argil, magnesia, soda, oxyd of manganese, and some water. For an account of it, see Pliny (H. N. xxxvi, 42.) He recommends it in diseases of the eyes. It appears evident, however, that he had copied from his contemporary, to whom he is so frequently indebted, we mean Dioscorides, who gives a similar description of pumice, and also recommends it in diseases of the eyes, more especially in opacity of the cornea, and likewise as an ingredient in applications to sores, and as a dentifrice. (v, 124.) Galen, after some preliminary discussion whether pumice be a metal, a stone, or an earth, proceeds to state its medicinal properties, in which he agrees with Dioscorides, most especially commending it as a dentifrice. (De Simpl. ix.) We may just mention in this place that modern authorities do not think so highly of this substance as a dentifrice. See Jameson’s ‘Mineral.’ (i, 333.) The Arabians under this head merely copy from Dioscorides and Galen. See in particular Serapion (De Simpl. 417.) Pumice anciently was used for polishing the leather with which books were bound. (Catullus, Epig. i.) Theophrastus (De Lapidibus), states that pumice is formed by the action of fire; and M. Dolomieu suspects that it is a vitrified granite or gneiss. The pumice, for some time past, has ceased to hold a place in our Dispensatory. Neither is it to be found in the modern Greek Pharmacopœia. Κιστὸς ἤ Κίσσαρος, Cistus, _Rock-rose_; it is an astringent shrub, and of gently cooling powers. Its leaves and shoots are so desiccative as to agglutinate wounds; but the flowers are of a more drying nature, being about the second degree, and hence when drunk they cure dysenteries and all kind of fluxes. Externally they relieve putrid ulcers. * * * * *