Salted herrings became an acknowledged form of tax or tribute, as also a medium of exchange for inland produce, and it was the value of these small fish that really first roused the cupidity of the inland dweller and caused them to compete with and finally oust the pagan Slav. And Wisby for a time was their great emporium, whence they extended their power, founding among other towns Novgorod on the Lake of Olm. It was to Wisby that association dues were paid; it was in Wisby that common money was deposited. They were kept in the German Church of Our Lady Maria Teutonicorum. For the churches in those times were buildings as much secular as religious, being not only places of worship, but also banks, storehouses, market-places, and sanctuaries. Four aldermen, selected from important cities of the League, namely, Wisby, Lübeck, Soest, and Dortmund, had each a key to the common treasure. The rules laid down in common council, over which these aldermen presided, and whose execution they enforced, were stringent in the extreme. For example, according to an old principle of Teutonic laws, a city was made responsible if a trader suffered malignant shipwreck or was robbed of his goods within its domain, and if these things occurred they were bound to help the sufferers to recover their goods or safety. That it was not always an easy task for the towns to execute this command may be gathered from the fact that in the earliest times even the Church looked on flotsam and jetsam as its legitimate dues; indeed, the revenues of some monasteries and churches were distinctly founded on this. Even Papal authority, even excommunication in later days, could not for a long while break the force of a barbarous and cruel custom. All the booty the waves cast on the shore was designated by the well-sounding term of _strandgut_ (property of the shore), and was regarded as a gift from Providence. The dwellers on the Baltic shore held so naïve a belief with respect to this matter that in their daily prayers they innocently asked God to give them a good harvest of _strandgut_. Lübeck in 1287, demanding from Reval, on the basis of its treaties, the restitution of stranded property, is told frankly by the governor of the city that "however many and long and large letters they may send him across the seas," yet his vassals would hold to the rights of their land, and "if," he adds, "on your letters or your prayers your goods are restored to you, I will suffer my right eye to be put out."