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Kaart van de Beneeden rivier de Maas en de Merwede, van de Noord Zee tot Gorinchem: de vyf blaaden v....

This map is a generalised and reduced version of the large survey map in six sheets, which Melchior Bolstra made of the Lower Maas and Merwede between 1738 and 1745. At that time, the Merwede had less and less water to swallow, which made it difficult to keep the river - and further downstream the Lower Maas to the mouth at the North Sea - at the required depth.

Bolstra's map was part of an attempt by the States of Holland to find a solution and involved a complete mapping of the entire basin of the Lower Maas and Merwede. The reason for this was the earlier closure of the kills in the Biesbosch, which caused the water levels in the Merwede to rise sharply. So much so, in fact, that the drainage of the polders was seriously impeded and the undyked areas between the channels were flooded. Moreover, the increased water pressure undermined the dams that had been erected, several of which broke through in 1739.

In order to get a clear picture of all the proposed hydrographical measures, a new mapping of the Merwede and the Lower Maas proved necessary. In 1738, Bolstra was commissioned to do so, but it took until 1746 before the map was completely finished. The mapping itself took place in 1738 and 1739, and the river measurements - the rivers on the map are marked with depth lines - between 1738 and 1741. The time was therefore spent in the engraving of the map by David Koster and the lettering by Jan van Jagen.

The reduced version of Bolstra's map appeared in 1749 and was intended for inclusion in Tirion's 'Hedendaegsche historie, of tegenwoordige staet van alle volkeren, dl. VII: Vervolgende de beschryving der Vereenigde Nederlanden, en wel in ’t byzonder van Holland'. The map also appears in Tirion's 'Nieuwe en beknopte Hand-atlas' of around 1750.