Note 9 — PRIVATE DIARY (continued 2)

Now in MS. Vespas. A. ii. art. 12, “Joannes Dee, 1555.” This is an extremely curious and valuable tract in the history of optical science, and is similar to the curious treatise by Gogava De speculo ustorio. The focus of the parabola is here for the first time indicated, a circumstance which has escaped the notice of scientific historians.