[225] PAGE 165, LINE 2. Page 165, line 2. _De pyxidis nauticæ vsitatæ compositione._--Gilbert's description of the usual construction of the mariner's compass should be compared with those given by Levinus Lemnius in _The Secret Miracles of Nature_ (London, 1658); by Lipenius in _Navigatio Salomonis Ophiritica_ (Witteb., 1660, p. 333); and with that given in Barlowe's _Navigators Supply_ (London, 1597). See also Robert Dudley's _Dell' Arcano del Mare_ (Firenze, 1646).
[226] PAGE 165 deals with the construction; the process of magnetizing by the loadstone had already been discussed in pp. 147 to 149. It is interesting to see that already the magnetized part attached below the compass-card was being specialized in form, being made either of two pieces bent to meet at their ends, or of a single oval piece with elongated ends. The marking of the compass-card is particularly described. It was divided into thirty-two points or "winds," precisely as the earlier "wind-rose" of the geographers, distinguisht by certain marks, and by a lily--or fleur-de-lys--indicating the North. Stevin in the _Havenfinding Art_ (London, 1599), from which work the passage on p. 167 is quoted, speaking on p. 20 of "the Instrument which we call the Sea-directorie, some the nautical box, ... or the sea compasse," mentions the "Floure de luce" marking the North.
The legend which assigns the invention of the compass to one Goia or Gioja of Amalfi in 1302 has been already discussed in the Note to page 4. Gilbert generously says that in spite of the adverse evidence he does not wish to deprive the Amalfians of the honour of the construction adopted in the compasses used in the Mediterranean. But Baptista Porta the Neapolitan, who wrote forty years before Gilbert, discredited the legend. "_Flavius_ saith, an Italian found it out first, whose name was _Amalphus_, born in our { 57} Campania. But he knew not the Mariners Card, but stuck the needle in a reed, or a piece of wood, cross over; and he put the needles into a vessel full of water that they might flote freely." (Porta's _Natural Magick_, English translation, London, 1658, p. 206.) See also Lipenius (_op. citat._ p. 390).
The pivotting of the needle is expressly described in the famous _Epistle_ on the Magnet of Peter Peregrinus, which was written in 1269. Gasser's edition, _Epistola Petri Peregrini ... de magnete_, was printed in Augsburg in 1558. In Part II., cap. 2, of this letter, a form of instrument is described for directing one's course to towns and islands, and any places in fact on land or sea. This instrument consists of a vessel like a turned box (or _pyxis_) of wood, brass, or any solid material, not deep, but sufficiently wide, provided with a cover of glass or crystal. In its middle is arranged a slender axis of brass or silver, pivotted at its two ends into the top and the bottom of the box. This axis is pierced orthogonally with two holes, through one of which is passed the steel needle, while through the other is fixed square across the needle another stylus of silver or brass. The glass cover was to be marked with two cross lines north-south and east-west; and each quadrant was to be divided into ninety degrees. This the earliest described pivotted compass was therefore of the cross-needle type, a form claimed as a new invention by Barlowe in 1597. The first suggestion of suspending a magnetic needle by a thread appears to be in the _Speculum Lapidum_ of Camillus Leonardus (Venet., 1502, fig. k ij, lines 25-31): "Nã tacto ferro ex una [=p]te magnetis ex opposita eius [=p]te appropinquato fugat: ut ex[=p]i[~e]tia docet de acu appenso filo."