20 INTERNATIONAL EXHIBITION, 1S76. 4. A brass model of the outer gate of the great sluices of Flushing harbor. 5. The reclamation of Haarlem Lake. On this subject seven maps were exhibited,—six showing the gradual formation of the lake from the action of the water of the separated ponds of 1531 upon the silty soil, reaching finally, in 1806, an area of about 43,000 acres, and stretching almost to the cities of Amsterdam, Haarlem, and Leyden, which it frequently threatened with destruction. The seventh map shows the whole tract protected by an enormous dike, and surrounded by a large navigable canal, its smooth floor divided by cross-canals and roadways into a populous cultivated area dotted over with houses and barns and containing two prosperous villages. Sections are given which show the construction of the dike and canal at dif ferent points, and suitable drawings show not only the construction of the engines and pumps by which the drainage was effected and by which it is maintained, but illustrate at the same time the almost universal practice of founding the heaviest structures on piles. 6. The steel swing-bridge at Dordrecht, with its somewhat original method of pivoting and support. 7. The denudation and protection of the sea-coast of North Holland. Here were shown the construction of the great “ Hondsbosch” and “ Petten” sea-dikes, which have a length of 5 kilometres. Both dikes are protected for nearly their whole length by a facing of basalt. The stone face of the Hondsbosch dike alone measures 13 hectares (or about 32 acres). These and the Helder dike, with the illustrations of the waste and subsequent protection of the coast at Egmont, con stitute in themselves a tolerably complete school of sea-embankment. In the exhibit, and in the accompanying documents, there is to Be found really all that has been learned by the centuries of active ex perience in connection with these enormous works, and the disastrous sea-action against which they are to serve as a protection. In the case of the town of Egmont, the present sea-line lies along the very heart of the town as it existed two hundred.years ago. More than half of the ancient city has been washed into the sea. The plans of the city in 1686 and 1718 show a strong fascine-made dike, and a large church and plaza. The map of 1875 shows that all these have been swept into the sea, a massive new dike protecting, it is hoped forever, the town, which has crept back farther from the shore. 8. The canal from Amsterdam to the North Sea. This is in some respects the largest work of its kind in Holland. It includes the construction of a broad and well-protected harbor, stretching three- quarters of a mile into the North Sea; an excavation through the ITS r . a. /
