And this brings us to the question, to how much of this Central German glass the term Bohemian may be fairly applied? This at least may be safely said, that the expression ‘German glass from the Bohemian frontier’ would cover nearly the whole of it. What it is essential to remember is that with the exception of a small section of the engraved glass we have little to do with Prague and the Czecs of the central plateau of Bohemia. As a whole this glass was made by German-speaking people dwelling on either side of the mountains which gird Bohemia to the north-east, the north-west, and the south-west, and divide that kingdom from Silesia, from Saxony, and from Bavaria respectively. Of all these districts it may be said that wherever the pines and beeches of the wooded slopes provided both fuel for the furnaces and (from their ashes) the indispensable potash, wherever, too, from the hillsides a pure white sand could be extracted, and finally, wherever in the mountain streams a source of power for cutting the wood or grinding the glass was at hand, there a glass furnace would sooner or later be established. 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?