Navigating at Sea

The people in the Middle Ages imagined the earth as flat as a pancake and surrounded by water. Above were the heavens and below water was hell. This is the reason why, when a large whale beached itself people thought it was a monster from the underworld and that it was a warning of imminent disaster. The Chinese and Arabs thought differently about the earth and the universe. Slowly that thought reached Europe. When Columbus set sail on his expeditions, the sailors were still scared of getting too far away from land in case they fell into a bottomless pit. Gradually it people started to believe that the earth was a sphere, that the moon revolved around the earth and the earth revolved around the sun.

When the first trips to Asia were made, people compared old Greek and Arab maps and cartographers kept adjusting them after every expedition. From stories about travelling to Russia, people began to understand that it may be possible to sail along the North Pole to Asia. For the Dutch that would be really handy because they could avoid Spanish ships and pirates while sailing past Dunkirk and North-Africa. Multiple times people tried to sail a northern route, however, the ships would get stuck in the ice and no-one will forget the story of Willem Barentsz, who had to survive the winter with his crew in harsh conditions on the island of Nova Zembla.

Plump fellow
The sailors were instructed to compare maps with the reality during the trips and make improvements wherever necessary. They pointed out points of interest and sketched coastlines so that the next VOC ships could identify mountains and bays. At their arrival the adjusted maps had to be immediately handed in at VOC offices to prevent them from falling into the hands of competing countries. To know where you were at sea, it was necessary to know the longitude and latitude. For that imaginary lines were drawn across the earth, which are shown on maps and globes. They would consider the shape of a plump fellow and his waistline would then be the equator. A width line runs towards set distances on the North and South Poles. On a certain day the sun and stars are at a predicted height. If you would measure the height of the sun around 12 o’clock at daytime or night you would be able to know what the latitude was at that moment.

Pole to pole
In the northern hemisphere the North Star was a clear beacon but isn’t seen in the southern hemisphere so by going to Asia they had to study the stars of the southern hemisphere too. The sailors learnt a rhyme, like one of the Psalms, which they used to remember the stars, which told them where they were. Measuring the longitude was incredibly difficult for the sailors. Longitude ran from Pole to Pole. In order to calculate this they needed to know the time at two different points. Nowadays, this is a relatively easy task, because we know the exact time and of course, travelling east, we keep adding an hour, because the sun rises earlier in the east.

Knotted rope
In the VOC days, navigation books just didn’t exist. One simply knew that the sun was at its height at noon, but they just didn’t know how much time there was between there and the next known longitude line on the map. Time was kept using hourglasses, which were turned every half an hour, after which the ship’s bell was rang and the number of “marks” were called. A “watch” lasted for approximately 4 hours or 8 “marks.” The speed was measured with a log, which was a triangle mounted on a leaden plate on the end of a knotted rope. The log was thrown overboard and an hourglass was turned which gave 15 and 30 second readings. The log remained upright in the water and the knots slipped through the hands of the sailor, who counted how many passed through his hand in the 15 second interval. Since then the speed of ships has always been measure in knots. Last but not least, they used a compass on board: a magnetised needle that always pointed to the North. A sounding lead was often used too, to measure how deep the sea was. This instrument was also a weighted rope with a series of knots. The lead at the base was hollow. They would often smear some grease onto this to pick up samples from the seafloor.

In short, finding your way at sea, back in those days was an incredibly complicated thing to do. You had to keep in mind all manner of storms at sea and indeed the monsoon winds. The sailors would receive lessons along the way. They would also make drawings, which would be later used and adjusted by cartographers and they would peruse books about the positions of the stars and about the depths of the sea in separate areas. Above all, it was always a question of experience. One often has a sense of wonder and awe for the sailors in the VOC days, who by studying the colour of the water, taking samples from the sea floor and studying the stars, could guess where they were in the world.

text: Ruud Spruit
translation: Jeffrey Jeltema, RSG Enkhuizen, tto-junior