* * * * *

THE SLEEPING SENTINEL.

  When the great Theban, in his midnight tramp,
    A sleeping guard beside the postern saw,
  He slew him on the instant, that the camp
    Might read in blood a soldier’s swerveless law.

  “Blame not your General!”—­pointing to the slain,—­
    The wise, severe Epaminondas said,—­
  “I was not cruel, comrades, for ’t is plain
    I only left him, as I found him, dead!”

IRON-CLAD SHIPS AND HEAVY ORDNANCE.

The new system of naval warfare which characterizes the age was proposed by John Stevens of Hoboken during the War of 1812, recommended by Paixhans in 1821, made the subject of official and private experiment here and in Europe during the last ten years especially, subjected to practical test at Kinburn in 1855, recognized then by France and England in the commencement of iron-clad fleets, first practised by the United States Government in the capture of Fort Henry, and at last established and inaugurated not only in fact, but in the principle and direction of progress, by the memorable action of the ninth of March, 1862, in the destruction of the wooden sailing-frigates Cumberland and Congress by the steam-ram Merrimack, and the final discomfiture of that powerful and heavily armed victor by the turreted, iron, two-gun Monitor.

The consideration of iron-clad vessels involves that of armor, ordnance, projectiles, and naval architecture.

ARMOR.

Material.  In 1861, the British iron-plate committee fired with 68-pounders at many varieties of iron, cast-steel and puddled-steel plates, and combinations of hard and soft metals.  The steel was too brittle, and crumbled, and the targets were injured in proportion to their hardness.  An obvious conclusion from all subsequent firing at thick iron plates was, that, to avoid cracking on the one hand, and punching on the other, wrought-iron armor should resemble copper more than steel, except that it should be elastic, although not necessarily of the highest tensile strength.  Copper, however, proved much too soft.  The experiments of Mr. E.A.  Stevens of Hoboken, with thick plates, confirm this conclusion.  But for laminated armor, (several thicknesses of thin plates,) harder and stronger iron offers greater resistance to shot, and steel crumbles less than when it is thicker.  The value of hard surfaces on inclined armor will be alluded to.

Solid and Laminated Armor compared.  Backing.  European experimenters set out upon the principle that the resistance of plates is nearly as the square of their thickness,—­for example, that two 2-inch plates are but half as strong as one 4-inch plate; and the English, at least, have never subjected it to more than one valuable test.  During the last year, a 6-inch target, composed of 5/8-inch boiler-plates,