(5.) The third rank, for many reasons, has been given to the smaragdus.[3009] Indeed there is no stone, the colour of which is more delightful to the eye; for whereas the sight fixes itself with avidity upon the green[3010] grass and the foliage of the trees, we have all the more pleasure in looking upon the smaragdus, there being no green in existence of a more intense colour[3011] than this. And then, besides, of all the precious stones, this is the only one that feeds the sight without satiating it. Even when the vision has been fatigued with intently viewing other objects, it is refreshed by being turned upon this stone; and lapidaries know of nothing that is more gratefully soothing to the eyes, its soft green tints being wonderfully adapted for assuaging lassitude, when felt in those organs. And then, besides, when viewed from a distance, these stones appear all the larger to the sight, reflecting as they do, their green hues upon the circumambient air. Neither sunshine, shade, nor artificial light effects any change in their appearance; they have always a softened and graduated brilliancy; and transmitting the light with facility, they allow the vision to penetrate their interior; a property which is so pleasing, also, with reference to water. In form they are mostly concave, so as to re-unite the rays of light and the powers of vision: and hence it is, that it is so universally agreed upon among mankind to respect these stones, and to forbid their surface[3012] to be engraved. In the case, however, of the stones of Scythia and Egypt, their hardness is such, that it would be quite impossible to penetrate them. When the surface of the smaragdus is flat, it reflects the image of objects in the same manner as a mirror. The Emperor Nero used to view[3013] the combats of the gladiators upon a smaragdus. CHAP. 17.—TWELVE VARIETIES OF THE SMARAGDUS. Of this stone there are no less than twelve different kinds; of which the finest is the Scythian[3014] smaragdus, so called from the country where it is found. None of them has a deeper colour than this, or is more free from defects: indeed, in the same degree that the smaragdus is superior to other precious stones, the Scythian smaragdus is superior to the other varieties. Next in esteem to this, as also in locality, is the smaragdus of Bactriana.[3015] These stones are collected, it is said, in the fissures of rocks, when the Etesian[3016] winds prevail; a period at which the earth that covers them is removed, and the stones are detected by their brightness, the sands being greatly agitated by the action of the winds. These last, however, are much inferior, they say, to those of Scythia in size. The third rank is held by the stones of Egypt,[3017] which are extracted from the hills in the vicinity of Coptos, a city of Thebais.