The working furnace, which is round, and generally built in the proportion of three yards in diameter to two in height, is divided into three parts, each of which is vaulted. The lower part, made in the form of a crown, contains the fire, which is never put out. Ranged round the circumference inside are the glass-pots or crucibles, in which the _frit_, or calcined _material_, is placed to be melted; and from several holes in the arch of the crown below issues a constant flame which, enveloping the crucibles, accomplishes the process of melting. Round the exterior of the furnace, you perceive a series of holes or mouths; these are called _boccas_, from the Italian, and it is through them the _frit_ is served into the crucibles and taken out when melted. The volume of heat is here so intense, that the _boccas_ are provided with movable collars or covers, generally composed of lute and brick, to screen the eyes of the workmen who stand outside in recesses formed for the purpose in the projections of the masonry. The severest part of the work arises when any of the pots, or crucibles, happen to become cracked or worn out, in which case the _bocca_ must be entirely uncovered, the defective pot taken out with iron hooks and forks, and a new one substituted in its place through the flames by the hands of the workman. In order to enable him thus literally to work in the fire, he is protected by a garment made of skins in the shape of a pantaloon, and heavily saturated with water. This strange garment completely covers him from head to foot, all except his eyes, which are defended by glasses. The material being now melted is fashioned into the desired forms by the hands of the workmen while it is yet hot, and then placed to cool gradually in the third furnace, or annealing oven, called the _lier_. This oven is a long, low chamber, heated at one end, and furnished with movable iron trays or pans, called _fraiches_ (from the French), upon which the various articles are set down, and finally removed, when they are sufficiently cold, through an opening which communicates with the _sarosel_, or room where the finished articles are kept.