Starting from the gorge of the Elbe above Dresden, to the east a complicated system of mountains covers the frontiers of Bohemia and Silesia. In the valleys that run down on either side glass has been made from the fourteenth century, if not before. It must not be forgotten that until it was seized by Frederick the Great in the eighteenth century Silesia had long been a dependence of the crown of Bohemia.[[191]]
To the west, beyond the gorge of the Elbe, the high plateau of Misnia falls abruptly on the Bohemian side, forming the Erzgebirge. Although for the glass of this district, the classical land of mining and metallurgy, we have no modern work to fall back upon, yet in the sixteenth century it produced two important writers on metallurgy and mining—Georg Agricola, the learned professor of chemistry, and the Lutheran divine Mathesius. Both of these writers have something to say upon the contemporary processes of glass-making.
At the western extremity of the Erzgebirge, on the one hand the Fichtelgebirge forms a link joining those mountains to the Thüringer Wald—these are both essentially German forest districts where much glass was made; on the other hand the Böhmer Wald runs south-east to the Danube. On the southern slopes of the latter range was made much of the glass that supplied the rich Franconian and Bavarian cities.
And the mention of these towns brings us to this difficult question: How far was the enamelling and the engraving of the finer specimens carried out in the mountain valleys where the glass was made, and how far in the workshops of the cities to which the undecorated glass had been transported?
For the northern districts at least Herr von Czihak has brought forward much evidence to show that the artists in the local towns carried back to the mountain furnaces, to be there fired, the glass that they had painted with enamel colours, and that even the finer kinds of engraving were done in the upland villages where water-power was abundant. This was certainly the case in later days in the famous centre of glass-engraving that grew up at Warmbrunn, in the Hirschberg district of Silesia. On the other hand much glass was, it would seem, enamelled in Dresden, and in the south the finer work both of the enameller and the glass-engraver was probably executed in the studio of the artist—at Nuremberg, for instance, or in other Franconian or Swabian towns.
For the German glass of the sixteenth century we have fortunately the two already mentioned contemporary writers, both of them Saxons by birth—Georg Agricola and Johann Mathesius. Agricola, it is true, ‘the founder of the sciences of mineralogy and metallurgy,’ in his famous work De Re Metallica,[[192]] devotes only a few pages at the end of his last chapter to the subject of glass; but here may be found the first accurate drawing of a glass furnace that has come down to us. Agricola mentions that he had passed two years at Venice, and had seen much of the glass-working when there.[[193]] Indeed, what he says of the materials, of the source of the alkali above all, seems to have relation to the Italian rather than to the German glass.
GERMAN GLASS FURNACE
SIXTEENTH CENTURY. FROM AGRICOLA
But this is not the case with the furnaces, which he describes and illustrates. Agricola distinguishes three separate ovens: the fritting oven; the main oven, where the glass is melted in pots; and an annealing oven for slowly cooling the glass. These ovens, however, may be combined in various ways in smaller works, reducing the number to two or even to one. The fritting oven is a detached building of beehive shape, which is also used for annealing the pots. The main oven, eight feet in height and ten feet in diameter, is of a similar outline. The wood is burned on the floor of a lower chamber, without any grating of firebars; the flame passes through into an upper chamber, around which are arranged eight pots, each two feet in height, with a working-hole in front of each pot. From the back of this chamber a passage opens which conveys the heated gases to the quadrangular annealing oven.