The sea-dyke saves Holland from the Northern Ocean, sombre and grey in its most genial mood, menacing and stormy for the long winter of our northern hemisphere; but it is to the inland dykes that protect the low-lying polders that Holland owes her prosperity and the sources of wealth which have made her inhabitants a nation. The original character of the country, a marshland intersected by the numerous channels of the Rhine and the Meuse, rendered it imperative that the System of dykes should be accompanied by a brother system of canals. The over-abundant waters had not merely to be arrested, they had to be confined and led off into prepared channels. In this manner also they were made to serve the purposes of man. High-roads across swamps were either impracticable or too costly; but canals furnished a sure and convenient means of transport and communication. At the same time they did not imperil the security of the country. Roads on causeways or reared on sunken piles would have opened the door to an invader, but the canals provided an additional weapon of defence, for the opening of the dykes sufficed to turn the country again into its primeval state of marshland. The occasion on which this measure alone saved Holland during the French invasion of 1670 is a well-known passage in history, and the hopes of the Dutch in resisting the attack of any powerful aggressor would centre in the same measure of defence, which is the submerging of the country, practically speaking, under the waters of the canals and rivers. There exists a popular belief that there is at Amsterdam one master key, a turn of which would let loose the waters over the land, but whether it is well founded or not no one except a very few officials can say. Pending any unfortunate necessity for breaking through the dykes and letting loose the waters, it may be observed in passing that the effectual maintenance of the dykes is a constant anxiety, and entails strenuous exertions. They stand in need of repeated repairing, and it is computed that they are completely reconstructed in the course of every four or five years. A sum of nearly a million sterling is spent annually on the work. A large and specially trained staff of engineers are in unceasing harness, a numerous band of dyke watchers are constantly on the look-out, and when they raise the shout, 'Come out! come out!' not a man, woman, or child must hold back from the summons to strengthen the weak points through which threatens to pass the flood that would overwhelm the land. It is a constant struggle with nature, in which the victory rests with man. As the dyke is the bulwark of Dutch prosperity in peace, it might be converted into the ally of despairing patriotism in war.