Sailing Toward Destiny

The various routes that VOC ships took to Batavia, first using the routes of previous Portuguese navigators and later the Seynbrief
It was a simple set of sailing instructions that inadvertently forced Dutch sailors onto Australia's western and southern shores in the 1600s.
Issued by the VOC (Dutch East India Company) on 15 August 1617, the Seynbrief, or Seylaesorder, virtually guaranteed that a Dutch ship would eventually make landfall somewhere on the coastline.
Its orders were basic. To cut an eight-to-12-month 8000-kilometre journey down to about six months, Java-bound ships were instructed to sail south from the Cape of Good Hope until they encountered the strong westerlies known today as the roaring forties. According to Article 12 of the Seynbrief, captains were to seek 'latitudes of 35, 36, 40 to 44° south, depending on where the seamen can find the best west winds'.
They were then instructed to sail east before the strong trade winds.
Article 13 provided the next step in the voyage: 'Now after the west winds have been found the ships should sail eastwards for at least 1000 miglen (about 7000 kilometres) before turning and laying their course for the north'.
If followed correctly, the northward heading would take them to their port in Java.
The instructions grew out of an idea by Hendrick Brouwer, a Dutch explorer and later Governor General of Batavia, who discovered the new course on a voyage to the East Indies in 1610. He had discovered the westerly trade winds between latitudes 35° and 40°S. Used to their full advantage, the strong and constant winds could shave up to six months off the eastward voyage.
Previously, Dutch traders had followed the route pioneered by Portuguese traders: sail round the Cape of Good Hope and up the east coast of Africa through the Mozambique Channel and across to India.
It was a long voyage. The Portuguese had established a well-fortified trading centre in Mozambique. To avoid the danger it posed, the Dutch ships sailed up the east coast of Madagascar, often as far as Mauritius, before setting a course to the Sunda Strait (between Java and Sumatra), all the time tacking into the prevailing south-easterly winds.
The winds suited the return voyage, but the outward leg proved slow going. Ships were becalmed for long periods beneath the hot sun: pitch between the planking melted and cargo rotted. Worse, the lack of fresh food and water exposed the crew to the dangers of scurvy.
Brouwer's alternative route was eagerly taken up by the VOC. It became not simply a preferred route from Europe, but the only one allowable.
The Seynbrief was, however, not as simple as it appeared: Dutch captains found it difficult to measure the distance along its eastward bearing. While sailors of the period could measure latitude (distance north or south of the equator), they could not accurately calculate longitude (distances east and west around the earth).
To measure the distances east and west, sailors used a variety of techniques. The method was, however, rough at best and more often than not crews had to resort to dead reckoning.
It was only a matter of time before a Dutch vessel would bump into the coast of the South Land. Hartog's voyage in 1616 was the first of many accidental discoveries.
