A note describing the structure and optical properties of a particular form of crystal, possibly that for which Haddington (Scotland) is known. This is dated from Oxford 17 May 1697. It is crowded to the right of the page by a large capital A, over which reads the citation, "La Theorie de la Manoeuvre des Vaisseaux. L'Example de la Manoeuvre des Vaisseaux de Monsr le Chevalier de Tourville". Beneath this is a note of an apparent eclipse of Mercury by the Sun (using Zodiac symbols) on 24 October 1697 (Julian calendar) and a bibliographic reference to an article in the Philosophical Transactions of the Royal Society for March 1691 (no 193).