A stone that feels the air

Conrad of Megenberg (1309–1374), a German scholar and cleric, introduces a stone he calls “jachant” in the sixth book of his Book of Nature. The reader is first invited to recognise the stone by its colour. The next observation already makes identification more difficult. A specimen that appears clear in one light can look dark under other conditions. What exactly has an observer seen when giving an account of its colour?

What “as people say” adds

The stone is yellowish, dark in darkness and clear in the light, for it feels the air, as people say.

– Konrad von Megenberg, Buch der Natur, 1861, p. 449.^[1]

Conrad might have been content to move the reader’s eye between light and darkness. Instead he lends the stone a verb that one might ordinarily reserve for someone capable of perception. It “feels” the air. Yet he also lets us hear how this explanation reached him. The words “as people say” come at the end of the same sentence. Readers can picture the change in appearance while recognising the point at which a received account enters the description.

A good specimen between extremes

Anyone choosing such a stone receives an unexpected piece of advice. The best specimen, Conrad says, is neither altogether dark nor altogether clear. Someone seeking the greatest brilliance could easily pass it over. Further on in the chapter he returns to its changing appearance. Now he contrasts a cloudy spell with a fine day. In effect, the reader has been given two views of the same object. It should still be possible to recognise it when it seems to have changed colour. That is part of the charm of this small description in a book arranged by kinds of stone.