and was movable round it, the two sights being fixed on one of the radii, and the measured altitude being marked by a plumb-line. The weighty mass was attached to a massive beam, vertically placed in a cubical framework of oak, and capable of being turned round by four handles, so as to place the quadrant in any vertical plane. The framework or base was strongly attached to beams sunk in the ground. There was no permanent roof over it, but some kind of removable cover. The instrument stood there for five years, until it was destroyed in a great storm in December 1574, and some observations made with it of the new star of 1572 and other fixed stars are published in Tycho's Progymnasmata.[1] He does not himself appear to have observed with it, although we possess his observations made at Augsburg, with few interruptions, from April 1569 to April 1570. Some of these are, as formerly, mere descriptions of the positions of the planets, stating with which stars they were in a straight line or in the same vertical; others are made with the cross-staff; others again with a "sextant" or instrument for measuring angles in any plane whatever, which he had designed about this time. This instrument, which he presented to Paul Hainzel, consisted of two arms joined by a hinge like a pair of compasses, with an arc of 30° attached to the end of one arm, while the other arm could be slowly moved along the arc by means of a screw.[2] We shall farther on describe this instrument in detail.
In addition to these instruments, Tycho while at Augsburg arranged for the construction of a large celestial globe five feet in diameter, made of wooden plates with strong rings inside to strengthen it. It was afterwards covered with
