The third dugout boat from Ostrów Lednicki

In the introduction, this paper refers to two previous actions aimed at extracting dugout boats from the bottom of Lake Lednica (in 1960 and 1982). The main part of the text presents the third action, carried out in 2016 by underwater archaeologists and students from the Department of Underwater Archaeology, Nicolaus Copernicus University. The paper explains the subsequent stages and procedures of investigations. All the difficulties and complications that arose from the circumstances of the deposition, the raw material from which the boat was made and the size of the object are emphasised. As shown by the 1997 study, the boat is made of wood from the lime tree. The boat is now 930 cm in length and 86 cm in width. The bow looks like a slightly oval pyramid; the stern was formed in the shape of a small overhang and could have been about 1 m longer. The dugout has three bulkheads: the first is the same height as the sides, the second one is shorter than the sides by about 6 cm and the third, formed stepwise (?), starts at the same height as the starboard and keeps this height to the crack, after which it is gradually lowered, going down about 5 cm below the port. The average thickness of the starboard is 5.5 cm, while the port is 4.5 cm thick. The thickness of the bottom at the stern break, ranges from 4 cm to 8.5 cm; in other breaks, it reaches as much as 19 cm. The dugout boat is poorly preserved. It has at least nine transverse cracks and one longitudinal crack ending at the first bulkhead. Part of the damage dated certainly back from the period of the destruction of the bridge; however, a thin layer of sediments covering the side or bulkhead wood did not protect the dugout from the anchors of modern fishing boats. The boat was dated using the C14 method (680 ± 120 BP); calibrated, this points to a very wide range of dates, between 980 and 1454. However, a stratigraphic analysis indicates that the boat fell to the bottom sometime between the period the bridge was completed (964) and the last major repair of the bridge captured by dendrochronological analyses (1023). The first stage of the action consisted in the underwater exploration of the bottom deposits with a water-type ejector. This was used for removing the sediments filling the inside of the boat and those within a belt of a small width on the outside of the sides of the dugout, so that they were clearly visible to a height of approx. 10 cm. The boat was filled with a layer consisting of a large number of strongly compacted chips, which produced a few artefacts: 11 potsherds, five bone fragments and a handle of a wooden cup that was preserved in two fragments. After the whole boat had been cleaned, underwater measurements were taken, which enabled the detailed drawing documentation of the dugout in situ. The second stage consisted in cleaning the area outside the boat with 25–30 cm wide and approx. 40 cm-deep trenches running along both sides of the boat and below them. The sides were cleaned gradually, in 2 m long-fragments, to prevent uncontrolled suction of the boat from the bottom and to reduce the possibility of accidental damage. After completing the exploration of each fragment, separated from the others with natural cracks, the released parts were slipped onto a properly prepared tin ‘trough’, surfaced using a buoyancy balloon and transported close to the shore.In the third stage of the campaign, special frames were prepared for each of the nine elements. After the individual parts had been put on the frames in water, they were brought to the surface with them, secured and transported to the Conservation Laboratory in Toruń. After completing all conservation and reconstruction procedures, the dugout boat will be made available to visitors at the Museum of Polish History in Warsaw