The “Slijkpraam”, which resembles the “Kromme Rijnaak” already mentioned, is used in the province of Utrecht, while finally, the “Vlotpraam” or “Slijkpraam” is still met with in Groningen.
From a certain standpoint, the “Hoogeveensche Pramen”, mentioned above, which are used in the peat bottoms, should be classified in this group.
THE “BAGGER- OR MODDERMOLEN” (The Dredge).
The “Moddermolen” (mud mill) or “Moddermolenschip” was already found in the first half of the XVIIth century, as the forerunner of the “Baggermolen” (bucket or ladder dredge). This dredge was worked by hand at first; later on horses were used for this purpose. (LE COMTE, p. 6, and WITSEN.) A horsepower and a stable were built on the deck. In the XVIIIth century, says LE COMTE, the old “Moddermolen” was already so perfected that it was imagined that there was nothing more to improve.
Navigation, however, kept calling for greater and greater depths, so that the Kater Brothers, dredge builders at Monnikendam, were led to build, in 1829, a boat which dredged down to a depth of 7 metres. From three to six horses were used, according to the depth and compactness of the materials to be dredged.
These same builders, says LE COMTE at another place, were the inventors of the “Klepschouwen”, for which they asked the concession on May 1, 1830. LE COMTE gives an engraving of these dredges in plate 12 of his work.
J. C. KERKMEIJER relates, in an article of the Eigenhaard Review (1906), entitled “De Diep-of Baggermolen, een merkwaardige ontdekking”, that he had found the model of the dredge built by its inventor in 1632, a model which is mentioned by C. A. ABBING, in his continuation of the Chronicle of Hoorn, by VELUIS (1841, p. 12), wherein it is stated: