Batavia's Graveyard - Mike Dash [200]
An additional problem lay in the fact that while lines of latitude run parallel, those of longitude get closer together the farther a ship sails from the equator. Navigating far to the south, along the borders of the Roaring Forties, the Batavia would traverse each degree of longitude considerably more quickly than would have been the case farther north. This made it even more easy to underestimate the distance run when sailing east across the Southern Ocean.
The Batavia would have carried four varieties of hourglass—a four-hour glass, for measuring the duration of watches, and one hour, 30 minute, and 30 second glasses. Later recalculation eventually revealed that in order to measure longitude correctly, the last-named glass should have contained 28 and not 30 seconds’ worth of sand, so Jacobsz’s calculations of longitude would have been 7 percent out even if he had been in possession of every other fact he needed. The only realistic option available at the time was to calculate longitude based on magnetic variation. The Dutch savant Petrus Plancius (1552–1622) developed a system of “eastfinding” that used this principle and published a table of variations for the guidance of mariners, but his results were insufficiently precise to guarantee accuracy.
The Dutch prime meridian Playford, op. cit., p. 31. At the time, it was popularly supposed that this was the highest mountain in the world.
Logs The English system, which involved a piece of wood attached to a long line, was considerably more accurate. Knots on the line allowed English sailors to assess the distance traveled in any given time with a greater degree of certainty. Green, The Loss of the VOC Retourschip Batavia, pp. 10–11.
“. . . it is in retrospect surprising . . .” One reason for the comparative excellence of Dutch navigation was the superiority of the VOC’s charts. The Dutch made great efforts to pool all available information, and returning skippers were required to hand over their journals and charts to the Company’s official mapmakers. The first mapmaker was appointed in the same year that the VOC was founded. Boxer, “The Dutch East Indiamen,” p. 87; Boxer, The Dutch Seaborne Empire, p. 164; W. F. J. Mörzer Bruyns, “Navigation of Dutch East India Company Ships around the 1740s,” The Mariner’s Mirror 78 (1992): 143–6.
Charts Dutch charts of this period were regularly updated to incorporate discoveries. A relatively complete map of the known South-Land coast by Hessel Gerritsz, the chief cartographer of the VOC, and dated 1618 (Schilder, op. cit., pp. 304–5), actually incorporates discoveries made off Australia up to 1628 and so could not have been available to Pelsaert when the Batavia sailed from Holland in the autumn of that year. Even this showed the Abrolhos as a long, thin string of islands and thus gave no real indication of their exact position or appearance.
Frederick de Houtman He came from Gouda, where he was born in 1571, and sailed with his brother in the first Dutch fleet to reach the Indies. Captured in battle in Sumatra, he learned Malay and on his release wrote the first Dutch-Malay dictionary. De Houtman was later governor of the Moluccas (1621–3). He died in Alkmaar in 1627.
Houtman’s Abrolhos De Houtman’s only comment was: “One should stay clear of this shoal, for it lies most treacherously for ships that want to call in at this land. It is at least 10 mijlen [45 miles] long; lies at 28 degrees, 26 minutes.” J. P. Sigmond and L. H. Zuiderbaan, Dutch Discoveries of Australia: Shipwrecks, Treasures and Early Voyages Off the West Coast (Adelaide: Rigby, 1979), p. 39. See also Schilder, op. cit., pp. 75–6, 100, 112–3. The seynbriefen of the VOC did mention the existence of the islands and warned seamen to beware of them.
Chapter 5: The Tiger
The material in this chapter