A story told by the chronicler Salimbene may, if rightly understood, show us that Michael Scot too, for all his astrological dreams, was a clever calculator and thus stood well in the line on which true advance in astronomy was even then proceeding. The Emperor asked him one day to determine the distance of the _coelum_, which probably means the height of the roof, in a certain hall of the palace where they happened to be standing together. The calculation having been made and the result given, Frederick took occasion to send Scot on a distant journey, and, while he was away, the proportions of the room were slightly but sufficiently altered. On his return the Emperor led him where they had been before and asked that he should repeat his solution of the problem. Scot unhesitatingly affirmed that a change had taken place; either the floor was higher or the _coelum_ lower than before: an answer which made all men marvel at his skill.[206] Greek science had taught the art of measuring inaccessible distances by means of angular observations, and this art was well understood by the Arabs. The _Optica_ of Ptolemy were already translated into Latin from an Arabic version by Eugenio, admiral to King Robert of Sicily during the twelfth century,[207] and mathematical instruments were known in that kingdom whereby angles could be taken and measured with some nicety. Scot must have possessed such an _astrolabe_ and the skill to use it with great delicacy, if we have rightly read the terms of the problem he solved so unhesitatingly. There is no cause for wonder then in the fact that, where pure and legitimate astronomy was concerned, this philosopher, who had won fame in his student days as the mathematician of Paris, who was now widely known as the translator of Alpetrongi, and who as a keen observer and ready calculator was well qualified for original research, should have taken a high place in these studies on his own account, and should have come to be acknowledged as a master in them. Even Bacon, who blamed Michael Scot so bitterly when language or philosophy were in question, speaks in a different way here, calling him a ‘notable inquirer into matter, motion, and the course of the constellations.’