On the Magnet/IV-11

Cardan's error when he seeks the distance of the
centre of the earth from the centre of the cosmos by the
motion of the stone of Hercules; in his
book 5, On Proportions.

Gilbert De Magnete IlloO.jpg
ne may very easily fall into mistakes and errors when one is searching into the hidden causes of things, in the absence of real experiments, and this is easily apparent from the crass error of Cardan; who deems himself to have discovered the distances of the centres of the cosmos and of the earth through a variation of the magnetick iron of 9 degrees. For he reckoned that everywhere on the earth the point of variation on the Horizon is always distant nine degrees from the true north, toward the east: and from thence he forms, by a most foolish error, his demonstrative ratio of the separate centres.