MURRHINA.	179
	Although this substance is continually alluded to by the writers of Roman imperial times as the most prized ornament of the dinner-table, yet the only description they have left us of its appearance and nature is that to be found in Pliny (xxxvii. 8). " The East sends us the Murrhina. They are found in several places, all little known, and lying within the Parthian dominions, but the finest sort in Carmania.* They are supposed to be formed from a liquid hardened by subterraneous heat. In superficial extent the pieces never exceed that required for a small dish (abacus), and in thick­ness seldom suffice for a drinking-cup like that just men­tioned (of Annius). They have a lustre without any strength, or rather a polish (nitor) than a lustre. But their value lies in the variety of their colours, the spots (or patches) suddenly turning themselves around into purple and opaque-white, and a third made up of both ; the purple, as if by a transition of hue, becoming fiery, or the milk-white part turning red. Some principally admire the extreme parts in them (i. e. the edges of the vases), and a certain play of colours like that seen in the rainbow." Hence Martial makes his amateur cry for " maculosoe pocula murrhas " (÷. 80). " Others prefer the spots to be opaque and fatty (pingues) : any transparency or paleness is con­sidered a defect. So are marks like salt, and warts, which