William Gilbert (1540-1603) is generally known for his De magnete of 1600, but as Sister Suzanne Kelly has shown in her work on his posthumous De mundo nostro sublunari philosophia nova (1651), the English physician entertained thoughts on a wider front than magnetism.' The dates of composition of the manuscripts of the De mundo have been determined by Sister Suzanne from internal evidence as sometime after 1590 for the first part, the Physiologiae, and the 1580s for the second part, the Meteorologia.2 She suggests that Gilbert was at work on the Physiologiae up until his death in 1603, although the latest dated reference is 1593.3 There is further internal evidence in the De mundo that reinforces Sister Suzanne's assumption that Gilbert was still working on the first part at his death and also suggests that he may have been revising the second part as well. In the Physiologiae, commenting on the new star of 1572, Gilbert says