As regards the development of sea power, it is not the total number of square miles which a country contains, but the length of its coast-line and the character of its harbors that are to be considered. As to these it is to be said that, the geographical and physical conditions being the same, extent of sea-coast is a source of strength or weakness according as the population is large or small. A country is in this like a fortress; the garrison must be proportioned to the _enceinte_. A recent familiar instance is found in the American War of Secession. Had the South had a people as numerous as it was warlike, and a navy commensurate to its other resources as a sea power, the great extent of its sea-coast and its numerous inlets would have been elements of great strength. The people of the United States and the Government of that day justly prided themselves on the effectiveness of the blockade of the whole Southern coast. It was a great feat, a very great feat; but it would have been an impossible feat had the Southerners been more numerous, and a nation of seamen. What was there shown was not, as has been said, how such a blockade can be maintained, but that such a blockade is possible in the face of a population not only unused to the sea, but also scanty in numbers. Those who recall how the blockade was maintained, and the class of ships that blockaded during great part of the war, know that the plan, correct under the circumstances, could not have been carried out in the face of a real navy. Scattered unsupported along the coast, the United States ships kept their places, singly or in small detachments, in face of an extensive network of inland water communications which favored secret concentration of the enemy. Behind the first line of water communications were long estuaries, and here and there strong fortresses, upon either of which the enemy’s ships could always fall back to elude pursuit or to receive protection. Had there been a Southern navy to profit by such advantages, or by the scattered condition of the United States ships, the latter could not have been distributed as they were; and being forced to concentrate for mutual support, many small but useful approaches would have been left open to commerce. But as the Southern coast, from its extent and many inlets, might have been a source of strength, so, from those very characteristics, it became a fruitful source of injury. The great story of the opening of the Mississippi is but the most striking illustration of an action that was going on incessantly all over the South. At every breach of the sea frontier, warships were entering. The streams that had carried the wealth and supported the trade of the seceding States turned against them, and admitted their enemies to their hearts. Dismay, insecurity, paralysis, prevailed in regions that might, under happier auspices, have kept a nation alive through the most exhausting war.