It is easy to see what a prolific nursery of seamen this Lake commerce must be, and how valuable a resource in a war with any great naval power. It is a resource which was wholly wanting to us in the War of 1812, when Commodore Perry had to bring his sailors from the seaboard with great difficulty and expense. In any future war with England, supposing such an unhappy event to take place, our great numerical superiority upon the Lakes in both vessels and sailors would not only insure our supremacy there, but also afford a large surplus of men for our ocean marine. But it may be said that these men are only fresh-water sailors, after all, and are not to be relied upon for ocean-navigation. We know there used to be a notion prevailing, that neither Lake vessels nor Lake men would do for salt water; but in 1856, the schooner Dean Richmond took a cargo of wheat from Chicago to Liverpool, beating a large fleet of ocean craft from Quebec across the Atlantic, and otherwise behaving so well as to cause the sale of the vessel in England. This voyage encouraged others to try the experiment, and in 1859 from thirty to forty Lake vessels loaded for ocean ports. That this trade will be very much increased there is no doubt, since it affords occupation for the Lake marine in the winter, when the Lake ports are closed by ice. On the western shore of Lake Michigan there are large settlements of Norwegians and Swedes, many of whom follow the Lakes as fishermen and sailors. Descendants of the old Northern sea-kings, they are as hardy and adventurous here as in their Scandinavian homes, and run their vessels earlier and later in the season than other men are willing to do. Science might have anticipated, however, that vessels built for fresh-water navigation, and loaded at Lake ports, would have an advantage on the ocean over those loaded on salt water. As is the density of the water of any sea, so is the displacement, or the sinking of the vessel therein. Therefore a vessel can carry a larger cargo in salt water than she can in fresh; and so, a Lake craft, loading at Chicago as deep as she can swim, will find herself, when she reaches the ocean, much more buoyant and lively. So, also, as, the more sail a vessel carries, the deeper she penetrates the water, it follows, that, the more dense the water, the more sail she can carry. In proof of these statements, the "Merchants' Magazine" tells us, that English vessels bound up the Black Sea take smaller cargoes than those going to the Mediterranean, because, the former being much less salt than the latter, vessels are less buoyant thereon, and can carry less. This difference in buoyancy will probably be enough to offset the higher seas and rougher weather of the Atlantic.