Having completed our examination of the ability of land batteries to cope, gun for gun, with a naval force, let us consider, for a few moments, the objection which is sometimes made to the use of fortifications for the defence of the sea-coast, viz.:  that our maritime cities and arsenals can be better and more economically secured by a home squadron.

We have already alluded to the impossibility of substituting one means of defence for another.  The efficiency of the bayonet can in no way enable us to dispense with artillery, nor the value of engineer troops in the passage of rivers, and the attack and defence of forts, render cavalry the less necessary in other operations of a campaign.  To the navy alone must we look for the defence of our shipping upon the high seas; but it cannot replace fortifications in the protection of our harbors, bays, rivers, arsenals, and commercial towns.

Let us take a case in point.  For the defence of New York city, it is deemed highly important that the East River should be closed to the approach of a hostile fleet at least fifteen or twenty miles from the city, so that an army landed there would have to cross the Westchester creek, the Bronx, Harlem river, and the defiles of Harlem heights—­obstacles of great importance in a judicious defence.  Throg’s Neck is the position selected for this purpose; cannon placed there not only command the channel, but, from the windings of the river, sweep it for a great distance above and below.  No other position, even in the channel itself, possesses equal advantages.  Hence, if we had only naval means of defence, it would be best, were such a thing possible, to place the floating defences themselves on this point.  Leaving entirely out of consideration the question of relative power, position alone would give the superior efficiency to the fort.  But there are other considerations no less important than that of position.  Fort Schuyler can be garrisoned and defended in part by the same militia force which will be employed to prevent the march of the enemy’s army on the city.  On the other hand, the crews of the floating defences must be seamen; they will consequently be of less value in the subsequent land operations.  Moreover, forts, situated as this is, can be so planned as to bring to bear upon any part of the channel a greater number of guns than can be presented by any hostile squadron against the corresponding portion of the fort.  This result can be obtained with little difficulty in narrow channels, as is done in most of the other works for the defence of New York, the works for Boston, Newport, Philadelphia, Baltimore, Charleston, Savannah, New Orleans, &c., and an approximation to it is not incompatible with the defence of the broader estuaries, like the Chesapeake.