'T Derde deel van 't Licht der zee-vaert, inhoudende de beschryvinghe der zeecusten van de Middelandtsche...

...according to an Italian compass, those aforementioned places lie a little more easterly than northeast, and a little more westerly than southwest; that is how the Italian sea charts are made. Further: Cape Passero in Sicily, and Cape de São João (the westernmost corner of Candia Crete) lie differently according to a Dutch compass, exactly east by south and west by north: but according to an Italian compass, east just as southerly, and west just as northerly, and so on with all other places.

Why the needles are not placed under the Fleur-de-lis, and are placed differently.

Although the reason why the needle is not placed under the compasses in one way in all places is known to many: we shall nevertheless write something about it for those who do not know. It is known by experience that the sailing needle, having been touched by the lodestone, points very differently at different places, as in some places exactly North, to others it deviates to the East, elsewhere to the West. As for example: By the islands of Corvo and Flores (being the westernmost of the Flemish Azores Islands), by Hjelmsøy west of the North Cape, by Cape Agulhas, and by the southern end of Celebes in the East Indies, the needle points (as one says) exactly North: But west of the Flemish Islands, east of the North Cape, by Novaya Zemlya, east of Cape Agulhas along the entire Indian Ocean, and in the Mediterranean Sea, east of the Venetian Gulf, it deviates to the west: And east of the Flemish Islands, west of the Cape of Good Hope, and in the Mediterranean Sea west of the Gulf of Venice, to the east. From this it is to be noted, that the deviation of the needle is twofold, namely, from the north to the west, which we call westeringh westerly variation: and from the North to the East, which we call oosteringh easterly variation. Each of these is again twofold, namely, Increasing and Decreasing Oosteringh; likewise Increasing and Decreasing Westeringh.

Increasing Oosteringh or Westeringh is that which increases as one sails from the West to the East; and decreasing, that which then decreases.

To explain the same a bit more broadly, we say thus, if one sails from the Island of Corvo (where the needle points exactly North) eastward; the needle begins (and gradually more and more) to deviate from the North to the East, until one sails the longitude of the Strait of Gibraltar, where it is at its highest (as one says) 13 degrees, that is Increasing Oosteringh. Continuing to sail along the Mediterranean Sea, it begins to decrease until near the mouth of the Venetian Gulf, where it disappears, and the needle again points exactly North: that is decreasing Oosteringh. From there continuing to sail eastward, the needle begins to deviate from the north to the west more and more, all the way to the end of the Mediterranean Sea, that is Increasing Westeringh. If one were to sail even further eastward...