d'Aulnoy, are confirmed by other authors. "In the broken banks south of the river," wrote Swinburne of the Manzanares at Madrid, "are found large quantities of pebbles, called Diamonds of Saint Isidro. They cut them like precious stones, and ladies of the first fashion wear them in their hair as pins, or on their fingers as rings. They have little or no lustre, and a very dead glassy water. The value of the best rough stone does not exceed a few pence." [103] "Jam vero et per Gallias Hispaniasque simili modo harenæ temperantur."--Pliny, Bk. xxxvi; Chap. 66. The chief centres of glass-making were Tarragona, several towns of Betica (Andalusia), and the Balearic Islands. It is chiefly in the form of imitation gems that specimens of the earliest Spanish glass have been preserved until our time,[104] although the characteristic of old Roman glass which is known in Italian as the _lattocinio_ or "milk-white" ornament, in the form of a thread or line carried all over the surface of a vessel, remains until this day a common feature of the glass of Spain, besides being found in Spanish-Moorish glass-work. [104] The distinction which Riaño attempts to draw between glass and glass paste is unsatisfactory. He remarks, too, that the manufacture of glass _may_ have existed in Spain at an earlier period than the last three centuries, but continues: "The earliest mention of glass-works in Spain will be found in Pliny, who, while explaining the proceedings which were employed in this industry, says that glass was made in a similar manner in France and Spain." Rico y Sinobas says that the rules for cutting glass by means of a diamond or _naife_ (as it was once called) are embodied in a treatise titled _El Lapidario_, originally written (perhaps in the fourth, fifth, or sixth century) in Hebrew, and which was brought to Spain some two or three hundred years later. This treatise was translated into Arabic by one Abolais, who lived at some time previous to the thirteenth century, and subsequently (in the year 1248, and by command of Alfonso the Learned) into the Castilian language.