What is "sound dues"

Sound \Sound\, n. [AS. sund a narrow sea or strait; akin to Icel., Sw., Dan. & G. sund, probably so named because it could be swum across. See Swim.] (Geog.) A narrow passage of water, or a strait between the mainland and an island; also, a strait connecting two seas, or connecting a sea or lake with the ocean; as, the Sound between the Baltic and the german Ocean; Long Island Sound.

The Sound of Denmark, where ships pay toll.
--Camden.

Sound dues, tolls formerly imposed by Denmark on vessels passing through the Baltic Sound.

The Sound Dues (or the Sound Toll; ) were a toll on the use of the Sound which constituted up to two thirds of Denmark's state income in the 16th and 17th centuries. The dues were introduced by King Eric of Pomerania in 1429 and remained in effect until the Copenhagen Convention of 1857.

All foreign ships passing through the strait, whether en route to or from Denmark or not, had to stop in Helsingør and pay a toll to the Danish Crown. If a ship refused to stop, cannons in both Helsingør and Helsingborg could open fire and sink it. In 1567, the toll was changed into a 1-2% tax of the cargo value, providing three times more revenue. To keep the captains from understating the value of the cargo on which the tax was computed, the elegant solution was chosen to reserve the right to purchase the cargo at the value stated.

In order to avoid ships simply taking a different route, tolls were also collected at the two other Danish straits, the Great Belt and the Little Belt; sometimes non-Danish vessels were forbidden to use any other waterways but the Øresund, and transgressing vessels were confiscated or sunk.

The Sound Dues remained the most important source of income for the Danish Crown for several centuries, thus making Danish kings relatively independent of Denmark's Privy Council and aristocracy. However, the dues were an irritant to nations engaged in trade in the Baltic Sea, especially Sweden. Sweden had initially been exempted from the dues at the time of their introduction because it was then in the Kalmar Union along with Denmark. However, after the Kalmar War and the Treaty of Knäred in 1613 Denmark introduced dues on cargoes from Sweden's Baltic possessions and on non-Swedish ships carrying Swedish cargo. The friction over the Dues was an official casus belli of the Torstenson War in 1643.

In 1658, Denmark had to cede her provinces east of the sound ( Scania, Halland, Blekinge, Bohuslän, and the island of Ven) to Sweden as a consequence of the Second Northern War. Thus, the toll could not be enforced as well as before but Denmark retained its established right of the dues. Swedish shipping became exempt from the Sound Dues by the terms of the Treaty of Copenhagen, signed on 27 May 1660. The exemption was rescinded after Sweden's defeat in the Great Northern War and the Treaty of Frederiksborg of 1720, although the eastern shore of the Sound was now Swedish.