only difference between them consists in this, that in the first a bar leading to the anchorage, reducing the depth of water to 12 feet at low tide, was omitted.  In neither case could frigates enter, though sloops of war of larger size might.  The whole scope, however, of this reasoning turns on a different principle—­on the works necessary to defend that bay and, by means thereof, New Orleans, the Mississippi, and all the surrounding country against a powerful invasion both by land and sea, and not on the precise depth of water in any of the approaches to the bay or to the island.

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.

On the important subject of our defenses generally I think proper to observe that the system was adopted immediately after the late war by Congress, on great consideration and a thorough knowledge of the effects of that war—­by the enormous expense attending it, by the waste of life, of property, and by the general distress of the country.  The amount of debt incurred in that war and due at its conclusion, without taking into the estimate other losses, having been heretofore communicated, need not now be repeated.  The interest of the debt thus incurred is four times more than the sum necessary, by annual appropriations, for the completion of our whole system of defense,