Heavy guns; Armor-clad casemates; Disappearing gun carriages in earthworks; Heavy mortars; Submarine mines or fixed torpedoes; and Fish torpedoes. The lecturer said that this nation may be attacked in four ways: First, by fleet and army combined, as in our revolutionary war; second, by blockading the entrances to all our ports; third, by bombardment of our seaport cities from a long distance; fourth, by a fleet forcing its way into our harbors, and making a direct attack or levying tribute on our people. The first is not now greatly to be feared. We are too distant from great powers, and too strong on land. The second should be met by the navy, and is, therefore, outside a discussion of coast defenses. The third is not probable, though it may be possible. The extreme range of 10 miles for heavy guns cannot be obtained from shipboard, and as an elevation of only 15° or 16° can be given, not over 5 to 6 miles range is attainable. The fourth is the one which is possible, probable, even certain--if we have war before we have better defenses. The race between guns and armor began about thirty years ago, and there has been more development in ships and guns in that time than in the two hundred preceding years. The jump has been from the 7 in. rifle as the largest piece to the 110 ton Armstrong; in armor, from 4½ in. of iron to the Inflexible with 22 in. of steel plating. The new Armstrong gun of 110 tons, tried only recently, with 850 pounds of powder and an 1,800 pound shot can pierce all the targets, and so far guns have the victory over armor. This gun developed 57,000 foot tons of energy, and will probably reach 62,000. Imagine the Egyptian needle in Central Park, shod on its apex with hard steel, dropped point downward from the height of Trinity steeple; it weighs 225 tons, and it would strike with just about the effect of one of the 110 ton gun's projectiles. Two of these guns are ready for the ironclad Benbow, and the Italians have several equally powerful of 119 tons from Herr Krupp. The most powerful gun in the United States, the 15 in. or the 12 in. rifle, has a muzzle energy of 3,800 foot tons. Ships like the Inflexible are the most powerful afloat. A steel water-tight deck extends across the ship, and she has 135 water-tight compartments. Her guns and engines amidships have a protection of 24 in. of armor, and amidships she has a citadel carrying two revolving turrets, each containing two 80 ton guns. Her turret armor is 18 in. thick. She can make 14 knots, and she has cost $3,500,000. But she has a low freeboard, and the guns, therefore, get no plunging fire. The French ship Meta has her heaviest guns mounted _en barbette_, high above the water line, giving a splendid plunging fire. Either of these ships could enter any of our harbors and hold us at her mercy.