This use of it then has been retained through every age to the present time, and it is mentioned by all those authors who have written on glass-making. Avicenna[570] makes so complete a distinction between it and the magnet, that he treats of each in a particular section, though he says nothing of its employment in the glass-houses; but indeed as a physician he had no opportunity of doing so. Albertus Magnus[571], however, who lived a century later, Roger Bacon, Basilius Valentine, Camillus Leonardus, Biringoccio, Mercati, Neri and many others have spoken in the plainest terms of this application. It is seen by the words quoted from different authors, that the name, which as far as I know occurs first in Albertus Magnus, was written in a great many different ways: _magnesia_, _magnosia_, _magnasia_, _manganensis_, _mangadesum_, and in French _magalaise_, _méganaise_, _magnese_. One might imagine that it is derived from magnet, partly on account of the similarity of the two substances, and partly on account of its supposed power to attract glass. Besides, its other name _sidera_ seems to have a reference to the Greek word for iron. Mercati, however, deduces the term from _mangonizare_, because potters besmear their wares with this mineral; but I suspect that the name was common before that use of the substance was known. It is to be observed that to this word various other significations have been given. Sometimes it seems to denote common iron-stone, and sometimes pyrites. What the gold-makers understood by it will be best discovered by consulting the works of their followers. _Braunstein_ also, the German name, the earliest mention of which occurs perhaps in the writings of Basilius Valentine, denoted at first every kind of ferruginous earth employed by the potters for painting. Thus Schwenkfeld gave the name of _Braunstein_ and _Braunfarbe_ to a kind of bloodstone[572]. For a long time the manganese imported from Piedmont was in Germany accounted the best, and therefore was much sought after by the artists of Nuremberg. Afterwards, a kind brought from Perigord, a place in Guyenne, and named _pierre de Périgueux_, or _lapis petracorius_, was highly esteemed. Wallerius gives this as a peculiar species; and in my opinion he is right. Its distinguishing characters are, that it resembles a burnt coal or cinder; has a somewhat shining surface, and on the fracture appears to be finely striped and a little coloured. A piece which I have in my possession exhibits all these marks. This species has been mentioned by very few of the new mineralogists. Germany, however, for some centuries past has employed its own manganese, which even in the time of Biringoccio was sent as an article of commerce to Italy.