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64 thunder. It was five inches long, and of a stone harder than basalt, which in some parts of Germany was used instead of anvils. He also relates how near Jülich another stone was driven by thunder through an enormous oak, and was then dug up. Aldrovandus gives a highly philosophical view as to the formation of these stones. He regards them as due to an admixture of a certain exhalation of thunder and lightning with metallic matter, chiefly in dark clouds, which is coagulated by the circumfused moisture and conglutinated into a mass (like flour with water), and subsequently indurated by heat, like a brick.

Georgius Agricola draws a distinction between the Brontia and the Ceraunia. The former, he says, is like the head of a tortoise, but has stripes upon it, the latter is smooth and without stripes. The Brontia seems to be a fossil echinus, and the Ceraunia a stone celt, but both are thunderbolts. Going a little further back, we find Marbodæus, Bishop of Rennes, who died in the year 1123, and who wrote a metrical work concerning gems, ascribing the following origin and virtues to the Ceraunius—

It was not, however, purely from the belief of his own day that Marbodæus derived this catalogue of the virtues of the Cerauniæ, but from the pages of writers of a much earlier date. Pliny, giving an account of the precious stones known as Cerauniæ, quotes an earlier author still, Sotacus, who, to use the words of Philemon Holland's translation, "hath set downe two kinds more of Ceraunia, to wit, the blacke and the red, saying that they do resemble halberds or axeheads. And by his saying, the blacke,