General H.L. Abbott delivered a lecture before the Academy of Sciences in New York, on the evening of March 21, a summary of which is given by the Herald as follows:
According to General Abbott, the country needs for its coast defenses:
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.
The entrance to the harbor of Alexandria, Egypt, is about 5 miles across. At the time of the bombardment the protecting fortifications were situated at the east end, in the center, and at the west end. On the west there were mounted 20 modern guns of great size and power, and there were 7 others at the east end.
Although the Egyptians fought bravely, they did very little harm to the English fleet, while on the second day the defense was silenced altogether. Following the bombardment - as in Paris - came the reign of mob law, doing more harm than the shells had done; and it is a possibility that every such bombardment would be followed by such an overthrow - at least temporary - of all forms of law and order.
The ships that had silenced the Alexandria batteries - which had 27 heavy guns more than we have - could reach our coasts in 10 or 12 days, and we would have nothing to meet them.
Armor-clad casemates are beginning to take the place of masonry. A tremendous thickness of masonry is built up to the very embrasures for the guns in the steel-clad turrets. This (the Gruson) system has been adopted by Belgium, Holland, Germany, Austria, and Italy.
In 1882 England had 434 heavy modern guns behind armored shore batteries; besides these at home, she had 92 in her colonies, of which 13 were in Halifax and 11 in Bermuda - for our express benefit.
What we have are brick and stone casemates and earthworks. A sample granite casemate, with iron-lined embrasure, was built at Fortress Monroe, and 8 shots were fired at it from a 12 in. rifle converted from an old 15 in. smooth bore. This gun develops only 3,800 foot tons of energy - a mere nothing compared with the 62,000 foot tons of the English and German 110 ton guns.
General Abbott showed most conclusive proof of the worthlessness of masonry forts in pictures showing the effect of the shots. The massive 8 feet thickness of granite was pierced and battered till it looked like a ruin. Not a man inside would have been left alive.
He also showed a "disappearing" gun in an earthwork, the gun recoiling below the level of the parapet and being run up to a firing position by a counterweight. In 1878 Congress stopped all appropriations for defenses, and nothing had been done since.
General Abbott said that we needed submarine mines or fixed torpedoes, which should be thickly interspersed about the channel and be exploded by an electric battery on shore. To prevent these torpedoes from being exploded by the enemy, the surface over them should be covered by plenty of guns. Heavy guns and mortars were needed to resist attacks by heavy iron-clads. Movable torpedoes were valuable, but only as an auxiliary - a very minor auxiliary - compared with submarine mines. We should be cautious not to infer that torpedoes made a satisfactory defense alone, as they must be protected by large and small guns, and they form only a part of the chain of general defenses.