To attain its extreme range a gun must be given an elevation of about fifteen degrees.  The greatest elevation given any of the guns on shipboard is about six degrees.  This limit is made by two factors—­the size of the portholes or opening in the turrets for the larger guns, and the danger of driving the gun backward and downward through the deck by any greater elevation.  The practical range of the great guns of a ship, the ten, twelve, and thirteen-inch, is not, therefore, believed to be over five or six miles, and even at that range the chances of hitting a given object would be very small.  A city could, of course, be bombarded with, effect at such a range, since a shell would do tremendous damage wherever it might strike, but a city to which a ship could approach no nearer than say seven miles would be safe from bombardment.

The muzzle velocities given the shells from the guns of the navy are something tremendous, while the muzzle energy is simply appalling.  The shell from the thirteen-inch gun leaves the muzzle at a velocity of 2,100 feet a second, and with an energy of 33,627-foot tons, or the power required to lift one ton one foot.  From this velocity the range is to 1,800 feet a second in the one-pounder, although from the three-pounder at 2,050 feet it averages about the same as the thirteen-inch.  The five-inch rapid-fire gun has the greatest muzzle velocity at 2,250 feet.  The muzzle energy is, of course, small in the smaller guns, being only twenty-five-foot tons in the one-pounder and 500 tons in the fourteen-pounder.

The power of penetration has already been given in a general way, but the power of penetration of steel is much greater.  At its muzzle velocity the thirteen-inch shell will penetrate 26.66 inches of steel, the twelve-inch, 24.16 inches; the ten-inch, 20 inches, and the five-inch, 9 inches.  The one-pound shell bursts in piercing one-fourth and nine-sixteenths-inch plates, scattering its fragments behind the target.

It may be interesting to note that the cost of one discharge of a thirteen-inch gun is $800, and that when a battleship like the Massachusetts lets loose her entire battery, both main and secondary, the cost of a single discharge is $6,000.

CHAPTER XXXIX.

Battleships and troops begin to move.

The North Atlantic Squadron Sent to Key West—­Commodore Schley at Hampton Roads—­The Voyage of the Oregon—­The Camp at Chickamauga—­ Where the Initial Work of Mobilizing the Troops Was Done—­Life at Camp Thomas—­Life on the Famous Battle Field—­Rendezvous at Fort Tampa—­The Great Artillery Camp.

Immediately following the action of Congress authorizing the President to call into service the army and navy of the United States, the North Atlantic squadron, under command of Captain Sampson, was mobilized at Key West.  It consisted of the following vessels:  Battleships Iowa and Indiana, armored cruiser New York, the monitors Puritan, Terror and Amphitrite, the gunboats Nashville, Castine, Machias, Wilmington and Helena, the cruisers Detroit, Cincinnati and Marblehead, and the torpedo-boats Cushing, Ericsson, Dupont, Foote, Winslow, Porter and Mayflower.