But it is to the works of the contemporary Italian writers that we had better turn for information on these practical points. These are of two classes:—1st, Works of some literary pretension which contain chapters on the glass of Murano for the information of the general public. 2nd, Technical treatises, consisting for the most part of formulas for the use of the glass-maker. To the first class belong Fioravanti’s remarks on mirrors, which we have already quoted. Biringuccio, the Sienese, in his treatise on _les arts du feu_ (_De la Pirotechnia_, Venice, 1540), has a chapter on glass (Bk. II. cap. xiii.). He tells us that the Venetians made glass from the ashes of _chali_, an herb that grows in Syria and also near Magalone, in the south of France (the lagoons of Maguelonne, near Cette). In the place of this _chali_ the ashes of fern or of the mysterious _duznea_ may be used. One part of the lixiviated ash is mixed with two of the _cogoli_, the clear white pebbles found in the bed of certain streams. To these materials a small amount of manganese is added, and the whole melted in a reverberatory furnace to form a substance known as _fritta_, already a kind of glass, but ‘_mal purgata_.’ The glass furnace is then described in some detail: it is made to hold eight crucibles (_conconi_), each three-quarters of a _braccio_ (say fifteen inches) in height. These _conconi_ are made with _terra di Valencia_, and are first well dried and annealed over the fritting-hearth. We are told how, after melting in these pots, the viscous substance is collected at the end of a hollow rod of iron, turned and returned upon the marver to unite the mass together, and then by blowing down the tube extended to form a vesicle. This ‘_vescicha_’ is now whirled round the head of the workman to lengthen it, or it may be pressed into a mould of bronze (‘_in un cavo di bronzo_’). It is now transferred to another rod of iron (the _pontella_, though the word is not used), worked up in various ways, and cut with shears. The handles and feet are added, and the vessel may be decorated by enamelling or otherwise.[161]