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

not along the straight east line I S, but north of it along the line I M K, as far as K. Continuing his course following the compass, he sails east-by-north instead of east, and finally arrives at the coast of Syria, not at B, the desired place, but far to the north of it at a higher latitude, at R.

If one were to sail back west from R, according to the aforementioned compass, one would return to A via the same route R K I, or if one sailed west from B towards Malta with such a compass, one would be led along T V to V V, just as far south of Malta as one had drifted north of B when sailing from Malta to B.

However, if one sailed west from B according to a compass that pointed exactly north at B, one would be led with such a course along B X Y to Z, just as far north of Malta as one had arrived south of it at V V with the aforementioned compass. All this is clear enough through the previous explanation.

Just as one reaches more and more northerly positions while sailing east with increasing westeringh westerly variation, as it seems according to the compass, so does this also happen in places where one has decreasing oosteringh easterly variation, such as in the part of the Mediterranean Sea to the west of the Venetian Gulf. This can be understood through the previous figure as follows: Assume A is Cabo Palos in Spain, and B a place near

Sicily, at equal latitude. If one were to sail east from A to B with a compass that pointed exactly north there, one would at first sail east without noticeable difference, but since the needle at C, by Palos, deviates almost a point from the north towards the east, and as one sails eastward, its deviation decreases, so that when the ship reaches the longitude of G, the Lily the north-pointing fleur-de-lis on a compass card which first pointed north at A now deviates towards the west, as from E to Q, and the east point towards the north, as from I to M; the ship (following the compass) would not be led along the straight east line A I to I. Continuing to sail, instead of coming to D, it would for the same reason come to K, and finally not to B, the desired place, but to R, far to the north of it at a higher latitude.

If one sails with increasing oosteringh easterly variation or decreasing westeringh westerly variation, one will, on the contrary, always fall further south in latitude than the compass indicates while sailing east. And although this does not happen in the Mediterranean Sea (since, as has been said, one finds there only decreasing oosteringh and increasing westeringh), we shall nevertheless write something about it for the better instruction of this business, and explain our point with a figurative example thus: