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The cog

The time and the concept of the cog

In the period from the 13th to the 17th century, the Hanseatic League – an organisation which connected large trade cities and included cities from Norther Germany, the Netherlands, Livonia, and Scandinavia – was operating in the Baltic Sea region. Even though the cities included in the League were mainly in contact with one another with the help of ships, there are very few medieval wooden vessels preserved.

A cog is a sailboat which was very common in Norther Europe in the Middle Ages and was used as a cargo vessel as well as a warship. The vessels were large, with a spacious cargo space, and were mostly equipped with one mast and one large square sail. Cogs also exhibited several other structural peculiarities which clearly set them apart from other vessels used at the time.

Discovery of the wreckage of the cog

Historical chronicles about Tallinn include several entries of storms which demolished port buildings and threw vessels ashore and there are places in the territory of today’s port which are known to conceal the remains of vessels. Thus, archaeologists were not extremely surprised when wreckages of two vessels were found in the territory of the former amusement park in Kadriorg in the course of the construction of two residential buildings in 2015.

Only a section of the bottom and of the left broadside were found of the vessel which was excavated first and was named the wreck of Viljo. Based on the analyses conducted to determine the age of the wood, the clinker-built vessel was probably built in the end of the 15th century.

The second vessel was discovered in the course of installing a sheet wall in the foundation pit when the excavator unexpectedly hit elements of a wooden vessel. The shipwreck was named Peeter after the driver of the excavator. At first, the shipwreck seemed to be seriously destroyed – only some elements from the side of the vessel and some larger pieces of the hull were found and it was assumed that there were two wreckages instead of one. Digging deeper, however, the contours of the 18 metres long and 6 metres wide roomy vessel started to take shape.

The finds which came with the cog

The more soil was removed from the surface of the wreck, the more surprises the vessel offered. Ceramic dishes, tools, leather gloves, footwear, and other pieces (apparently of clothing) were found in and around the vessel. It was found that the vessel had been divided in three rooms with the help of two partition walls. Some burnt bricks, fishbones, a wooden barrel, a stone brayer, and a grinder for grinding grain were discovered from the room in the stern end. The galley of the vessel was probably located there which was most likely used for storing food products and cooking meals for the crew. The cargo was probably stored in the largest room of the vessel, the hold, which contained wooden barrels with fishbones.

Most of the clay dishes found from the ship had been made in Germany and originate from the 14th century, according to experts. 16 samples were taken from the vessel in order to date it and were analysed in the laboratories of the University of Tartu. It was found that the wood used to build the vessel (oak and pine) had been cut in the end of the 13th century, probably in the territory of today’s Poland. Thus, the vessel may have already been built in the beginning of the 14th century.

The vessel which is believed to have mainly sailed the Baltic Sea went down near Tallinn in the first half of the 14th century, that is in the period when Tallinn was actively trading with other cities. The shape of the vessel also indicates that it used to sail between the trade cities of the Hanseatic League back in the day.

The significance of the finds

After cleaning of the hull of the vessel of soil, the assumptions found proof. The broadsides of the vessel were clinker-built, but the bottom was carvel-built. Wooden pins had been used to attach the planks to the frame which were punched through the edges of the planks and the sharp of the pins which protruded from the wood was turned and punched into the plank from the inside. Moss had been used to seal the vessel which was held in its place by wooden strips. Small metal brackets which had been used to attach the strips were also found in the course of cleaning the broadside. In the hold of the vessel, the keelson and the base of the mast were found which held the mast of the vessel and the large square sail. All the features described, as well as the wide and flat fin of the vessel and the strait stern indicate that the vessel was a cog.

The importance of cogs for the medieval trade on the Baltic Sea is hard to overestimate. Just like today, it was most reasonable to transport large amounts of cargo by sea in the mediaeval times and this job was mainly performed by cogs in the era of the Hanseatic League. Researchers have stated that the network of large trade cities and routes would probably have never come to be without cogs. Thus, cogs were true work horses which delivered fur and wax from Russia and all kinds of goods from expensive spices to fish, beer, and wine from German cities. One of the main articles of trade was the salt from Lüneburg and Baye with shiploads of it transported east. Trading with salt was also one of the sources of wealth for Tallinn with hundreds of cogs probably passing the port of Tallinn throughout the years. Thus, for an age-old trade city like Tallinn, finding a cog is probably as remarkable as finding a Viking ship from the island of Saaremaa would be. For the first time, we get to take a first-hand look at a cog which delivered goods to the medieval Tallinn – a type of vessel which helped to give Tallinn the shape which we see today.

Check out the books

Roio, M. et. al., 2016. Medieval ship finds from Kadriorg, Tallinn. – Archaeological Fieldwork in Estonia 2015, 139–158.

Roio, M. et. al., 2016. Uppunud vrakid Kadrioru maapõuest. – Muinsuskaitse aastaraamat 2015, 4–8.