Marine Fortification

This kind of fortification differs from land fortification in that the approaches of the enemy which are to be resisted take place on the level of the sea, so that he can come near without having to overcome the dangerous slope of the glacis. The combat is simply one between two powerful batteries, and the question to be decided is, whether the ship or the fort will first be placed hors de combat ; the ship having ordinarily the largest number of guns, while the fort has more solid battlements, and its fewer guns of great caliber can be fired with a steadine unattainable on so shifting a base as the ocean. Under these circumstances, the le relief a sea-fortre has the better, the le likely is it to be hit from shipping. Its walls are usually built perpendicular, or nearly so. The magazines and quarters for the men are bomb-proof, as also are the casemates, from which the guns are usually fired, although sometimes, as in the martello tower, the gun is worked on top of the structure. Sea fortifications may be of various importance, the simplest being the battery consisting of a mere parapet formed in a cliff or on a hill, and mounted with guns to command the sea; these are generally built in such concealed situations, that it is hoped the hostile ship will not perceive them until they actually open fire. These are numerous all around the British coast. Next greater in importance is the martello tower (which see). More powerful still are the breach-forts, such as those which on either shore defend the entrance to Portsmouth harbor, England. These are constructed of the most solid masonry, and armed with guns of the heaviest caliber, sweeping the very surface of the sea so as to strike an approaching ship between wind and water. The guns are usually in bomb-proof casemates, and the fort is often defended on the land side, if the coast be level; if, however, higher ground be behind, this would be usele , and then the sea-front alone is defensible. Most terrible of all sea-forts, however, are the completely isolated forts with perpendicular faces and two and three tiers of heavy guns. Such are the tremendous batteries which render Cronstadt almost unapproachable, and by which Spithead and Plymouth Sound, England, are now being fortified. These forts are generally large, with all the requisites for a garrison to maintain itself; against them wooden ships stand no chance, and in the American civil war, Fort Sumter, at Charleston, has shown itself no mean antagonist for ironsides. In the new forts, as Spithead, etc., iron is to be employed as the facing, in plates of such vast thickne and weight that it is supposed no ship can ever po e any comparable power; and as they are to be armed with guns the smallest of which will probably be 300-pounders, it is expected that they will be able to destroy any fleet that could be sent against them. At the present day, the value of sea fortifications is disputed, as iron-plated ve els may pa them with impunity, unle the artillery in the fort be so heavy as to destroy the armor of the ships. In the long run, however, it is apparent that the fort can command the greater power; for its armor may be of any thickne , while that of the ship must be limited by her floating powers, and on the other hand, the limit to the size of artillery must be sooner reached in a ship than in a solid and stationary fortre .