brass arc of 634 feet radius, 5 inches broad and 2 inches thick, fastened to the wall with strong screws, and divided in his usual manner by transversals; it was furnished with two sights, which could slide up and down the arc. At the centre of the arc there was a hole in the south wall, in which a cylinder of gilt brass projected at right angles to the wall, and along the sides of which the observer sighted with one of the sliding sights. This was one of the most important instruments at Uraniborg, and was much used. It is, therefore, no wonder that Tycho (who claimed it as his own invention) wished to fill the empty space on the wall inside the arc with a picture of himself and the interior of his dwelling. Tycho is represented as pointing up to the opening in the wall, and he says the portrait was considered a very good likeness; at his feet lies a dog, "an emblem of sagacity and fidelity." In the middle of the picture is a view of his laboratory, library, and observatory, and on the wall behind him are shown two small portraits of his benefactor, King Frederick II., and Queen Sophia, and between them in a niche a small globe. This was an automaton designed by Tycho, and showing the daily motions of the sun and moon and the phases of the latter. The portrait was painted by Tobias Gemperlin of Augsburg, whom Tycho had encouraged to come to Denmark; the views of the interior of Uraniborg by its architect, Stenwinchel; and the landscape and the setting sun by Hans Knieper of Antwerp, the King's painter at Kronborg. The picture bears the date 1587, but the quadrant itself had been in constant use since June 1582.[1]
Another instrument on which Tycho found room for a picture was his smallest quadrant, one of the earliest instruments constructed at Uraniborg. The radius of the
- ↑ There are a few meridian altitudes of Spica observed in April 1581, "per magnum instrumentum," which probably were also made with this quadrant.
