Rico y Sinobas has described a Spanish glass-oven of those primitive times. He says that such as were used for making objects of a fair size consisted of three compartments resting one upon the other; the lowest cylindrical, to hold the fire and ashes, the next with a domed top, for concentrating the heat, and the third and uppermost, which also had a domed top, for holding the pieces of glass that were set to cool by slow degrees. The wall of the oven contained a number of openings, which served, according to the level at which they were situated, for controlling the fire, adjusting the crucibles, or extracting, by means of metal rods, the lumps of molten glass, previously to submitting them to the action of the blowpipe. The dimensions of such of these primitive ovens as have been found in Spain or Italy, are nine feet in height by six feet in diameter, and the material of which they are built is argil, of a kind insensible to heat, and carefully freed by washing from all foreign, soluble, or inflammable substances. The crucibles, which were fitted in the oven two, four, or at most six at a time, were of this argil also, wrought and purified with even greater care. Ovens and crucibles of a smaller size were used for making diminutive objects such as beads and imitation precious stones.[105] [105] Rico y Sinobas, _Del Vidrio y de sus artifices en España (Almanaque del Museo de la Industria_, 1870). Almería was probably the most important centre of Spanish-Moorish glass-making, and is mentioned in connection with this craft by Al-Makkari. The oriental shape of the older vessels which were made in this locality is still preserved in certain objects such as jars, bowls, flasks, and _aguardiente_-bottles, which are still manufactured, or were so until quite recently, throughout a region extending from Almería to the slopes of the Alpujarra. "All these objects," says Riaño, "are decorated with a serrated ornamentation of buttons, trellis-work, and the lines to which I have already alluded, which were placed there after the object was made, in the Roman style. The paste is generally of a dark green colour, and when we find these same features in vessels of clear white glass, we may affirm that they are contemporary imitations made at Cadalso or elsewhere, for they are very seldom to be met with in the provinces of Almería and Granada, and are generally found at Toledo and other localities; it is, moreover, a common condition of oriental art that its general form complies with a geometrical tracery, and we never find, as in Italian works of art, forms and capricious ornamentations which interfere with the symmetry of the general lines, and sacrifice them to the beauty of the whole."