OVUM ANGUINUM.	257
	Pliny accurately distinguishes his Ophites marble from the Lacedemonian (Verde Antique), " of a very precious kind, and the most gay of all (hilarius)." A similar marble, named after Augustus and Tiberius, had been discovered in Egypt during their respective reigns. This serpentine Marble is a compound of Magnesia and Silica in nearly equal proportions, owing its colours to a small admixture of Iron oxide, and of Manganese, and Chrome. "When recent it is easily cut with the steel tool, but attains con­siderable hardness after exposure to the air, as is demon­strated by the excellent preservation of the plaques so plentifully introduced into the external inlaid decorative work of the Tuscan Gothic buildings. The Verde Antique has angular patches of pure white marble dispersed through­out an unmixed green mass, much resembling Plasma in its colour and slight translucency. The Ophites (Green Ser­pentine), on the contrary, is dull, opaque, and merely speckled with white, like the skin of the asp that gives the name. Pliny makes two kinds : the pale and softer, the dark of superior hardness. He notes that it did not afford columns, except of very small dimensions. In fact exist­ing remains show that the Romans used it chiefly in veneers for coating the walls of rooms, or for inlaying in their "pavimenta sectilia." The ancients evidently knew nothing of the quarries at Prato near Florence, which now furnish Green Serpentine, " Verde di Prato," in inexhaustible quantities, and employed by the Tuscan marble-workers for vases, inkstands, and similar artistic manufactures in great variety. The Red Serpentine of late years extensively quarried about the Lizard Point, Cornwall, and much used for the purpose of internal decorations, and for vases, is far superior to the Green in beauty. Its ground is red elegantly mottled with black, and it takes a fine and durable polish. Although