The reasoning which is applicable to the works near New Orleans and at the bay of Mobile is equally so in certain respects to those which are to be erected for the defense of all the bays and rivers along the other parts of the coast. All those works are also erected on a greater scale than would be necessary for the sole purpose of preventing the passage of our inlets by large ships of war. They are in most instances formed for defense against a more powerful invasion, both by land and sea. There are, however, some differences between the works which are deemed necessary in the Gulf and those in other parts of our Union, founded on the peculiar situation of that part of the coast. The vast extent of the Mississippi, the great outlet and channel of commerce for so many States, all of which may be affected by the seizure of that city, or of any part of the river to a great extent above it, is one of those striking peculiarities which require particular provision. The thinness of the population near the city, making it necessary that the force requisite for its defense should be called from distant parts and States, is another. The danger which the army assembled at New Orleans would be exposed to of being cut off in case the enemy should throw a force on the river above it, from the difficulty of ascending the river to attack it and of making a retreat in any other direction, is a third. For an attack on the city of New Orleans, Mobile Bay, or any part of the intermediate coast ships of war would be necessary only as a convoy to protect the transports against a naval force on their passage, and on their approach to the shore for the landing of the men, and on their return home in case they should be repulsed.