But simultaneously with the decline of the Spanish and Hanseatic Mercantile Marines was growing up the Dutch. And it cannot be emphasised too strongly that this was owing to the herring having in the fifteenth century begun to spawn in the North Sea instead of the Baltic, as already mentioned. It seems curious that an innocent fish should thus be the deciding force of international history. If you examine modern Dutch charts you will still see marked channels and shoals which show the intimate connection which that country had with fishing. The “haringvliet,” or mouth of the Maas, and the “Schotsman” shoal, off the island of Walcheren, at once suggest the time when the Low Countries were acquiring wealth by their fisheries and doing a good deal of trade with Scotland. Then they became more ambitious, and built those fine great ships, which you see in the paintings of Vroom and other artists, that were the means of bringing home from their East Indies wealth in another form once enjoyed by the Venetians and Spaniards. So invaluable had the fisheries been to the Dutch, both in regard to shipbuilding and in creating a fine school of seamanship, that by the time of Cromwell these Netherlanders were the “waggoners of the sea,” had the world’s carrying trade and owned four-fifths of all the merchant ships that sailed the seas. Now, having regard to the young, keen sea spirit which had made the sixteenth century so illustrious, it was hardly surprising that before long there should be trouble between the English and the Dutch. It was analogous to the years which immediately preceded the Great War of 1914. Collision was certain: it was a question only of time. Thus, as early as 1608, Grotius, the famous Dutch jurist, wrote his _Mare Liberum_, wherein he contended that the high seas were open to all. Contemporary with him was living the English jurist Selden, who in 1618 had begun his treatise _Mare Clausum_. At the request of James I it was not published for fear of complications with the Danes, but in 1635 Selden again took up this work at the desire of Charles I. In the previous year Charles began to levy ship-money, which really was intended in order to strengthen the fleet against the Dutch in the probability of war.