'With his sharp lok perseth the sonne': A new quadrant from Canterbury.

This paper describes a medieval instrument, a quadrans novus, which turned up during archaeological works in England. The invention of the instrument by Profacius in 1288 is discussed in terms of two other medieval instruments, the quadrans vetus and the common astrolabe. The characteristics of the present instrument are compared with those of the seven other known medieval quadrants. It is shown that the new quadrant was made in England for explicit use with the Sun. [ABSTRACT FROM AUTHOR]