A swarm of river vessels and fly-boats were coming daily through the rivers of Germany, France and the Netherlands, laden with the agricultural products and the choice manufactures of central and western Europe. Wine and oil, and delicate fabrics in thread and wool, came from France, but no silks, velvets, nor satins; for the great Sully had succeeded in persuading his master that the white mulberry would not grow in his kingdom, and that silk manufactures were an impossible dream for France. Nearly a thousand ships were constantly employed in the Baltic trade. The forests of Holland were almost as extensive as those which grew on Norwegian hills, but they were submerged. The foundation of a single mansion required a grove, and wood was extensively used in the superstructure. The houses, built of a framework of substantial timber, and filled in with brick or rubble, were raised almost as rapidly as tents, during the prodigious expansion of industry towards the end of the war. From the realms of the Osterlings, or shores of the Baltic, came daily fleets laden with wheat and other grains so that even in time of famine the granaries of the republic were overflowing, and ready to dispense the material of life to the outer world. Eight hundred vessels of lesser size but compact build were perpetually fishing for herrings on the northern coasts. These hardy mariners, the militia of the sea, who had learned in their life of hardship and daring the art of destroying Spanish and Portuguese armadas, and confronting the dangers of either pole, passed a long season on the deep. Commercial voyagers as well as fishermen, they salted their fish as soon as taken from the sea, and transported them to the various ports of Europe, thus reducing their herrings into specie before their return, and proving that a fishery in such hands was worth more than the mines of Mexico and Peru. It is customary to speak of the natural resources of a country as furnishing a guarantee of material prosperity. But here was a republic almost without natural resources, which had yet supplied by human intelligence and thrift what a niggard nature had denied. Spain was overflowing with unlimited treasure, and had possessed half the world in fee; and Spain was bankrupt, decaying, sinking into universal pauperism. Holland, with freedom of thought, of commerce, of speech, of action, placed itself, by intellectual power alone, in the front rank of civilization. From Cathay, from the tropical coasts of Africa, and from farthest Ind, came every drug, spice, or plant, every valuable jewel, every costly fabric, that human ingenuity had discovered or created. The Spaniards, maintaining a frail tenure upon a portion of those prolific regions, gathered their spice harvests at the point of the sword, and were frequently unable to prevent their northern rivals from ravaging such fields as they had not yet been able to appropriate.