The _Ostracites_ appears to have been petrified oysters. Dioscorides recommends it in menorrhagia, in inflamed breasts, and spreading sores. (v, 164.) Galen also recommends it for clearing the cornea. (De Simpl. viii.) See in like manner Avicenna (ii, 2, 393.) The _Geodes_ contains iron, argil, and silica. It is nearly allied to the Eagle-stone, and hence it is often called the Bastard Eagle-stone. See Hill’s ‘Theophrastus.’ Dioscorides recommends it as an ophthalmic remedy, and as a liniment for inflammations of the mammæ and testicles. (v, 168.) Avicenna says the vapour of vinegar in which it is dissolved checks the flow of blood and cures hot aspostemes. (ii, 2, 398.) Matthiolus confesses himself quite unacquainted with the _Naxian Whetstone_. Sprengel reckons it allied to the Smiris. Galen would rather seem to make it a variety of the Ostracites. The _Lapis Lyncurius_ of the ancients was our Jacinth or Hyacinth. See Beckmann, and De Laet, ‘de gemmis.’ Dioscorides recommends it in affections of the stomach and bowels. (ii, 100.) Serapion describes minutely the _Lapis iacinctus_, or hyacinth, but merely mentions of it that it was used as a seal to avert the thunderbolt. (c. 398.) The stone which he describes in the following chapter, would appear decidedly to be the Tourmaline. He calls it Lapis rubeus, _seu_, _hager albuzedi_. Used as a seal, he says it dispels bad dreams. The _Cos_ is composed of a schistose argil. The _Cos Olearia_ would appear to have derived its name from requiring the use of oil to answer the purpose of whetstone. See Pliny (H. N. xxxvi, 47.) It is impossible to determine accurately the nature of the _Hieracites_. Aëtius, who has given the fullest account of it, describes it as a darkish green stone. The _Indian-stone_ would seem to be identical with the Arabian-stone. Rhases (Cont. l. ult. 401.) The _Lydian-stone_ is ranked by Dr. Thomson as a sub-species of Flint-slate. He remarks that it was used as a touchstone by the ancients. The _Ætites_, or _Eagle-stone_, is a species of oxide of iron. Dr. Hill remarks that custom has given the name of ætites to every fossil that has a loose nucleus within it. The ancients used it very frequently as an amulet and incantation. See particularly Dioscorides and Aëtius. The Arabians also confirm, in the strongest terms, the imaginary efficacy of the Eagle-stone when used as an amulet. That it accelerated the delivery of woman in tedious labours, Serapion and Rhases declare, from ample experience, and that it would produce this beneficial effect on those who had faith in it _we_ can readily believe. Indeed, we have often regretted that such innocent modes of working upon the imagination of women in labour had given place to more dangerous methods of practice in such cases. The Eagle-stone was retained in the English Dispensatory with all its ancient characters as late as Quincy. (165.)