in the inhabited and vital parts of the vessel, of rendering the possible bursting of a gun comparatively harmless to the crew and ship, and of rapid manoeuvring, as compared with the turret system, besides all the advantages of the turret as compared with the casemate or old-fashioned broadside system.  The necessity of fighting at close quarters has been remarked.  At close quarters, musket-balls, grape, and shells can be accurately thrown into ordinary port-holes, which removes the necessity of smashing any other holes in the armor.

Protection at, and extending several feet below the water-line, is obviously indispensable around the battery of a vessel.  It is valuable at other points, but not indispensable, provided the vessel has numerous horizontal and vertical bulkheads to prevent too great a loss of buoyancy when the vessel is seriously damaged between wind and water.  Harbor-craft may be very low on the water, so that only a little height of protection is required.  But it is generally supposed that sea-going vessels must be high out of water.  Mr. Ericsson’s practice, however, is to the contrary; and it may turn out that a low vessel, over which the sea makes a clean breach, can be made sufficiently buoyant on his plan, If high sides are necessary, the plan of Mr. Lungley, of London, may be adopted,—­a streak of protection at the water-line, and another forming at the top of the battery at the top of the structure, with an intermediate unprotected space.  A shot-proof deck at the water-line, and the necessary shot-proof passages leading from the parts below water to the battery, would of course be necessary.

Considering the many expedients for vastly increasing the thickness of armor, the idea, somewhat widely expressed, especially in England, that, in view of the exploits of Armstrong, Clay, and Whitworth, iron-protection must be abandoned, is at least premature.  The manner in which the various principles of construction have thus far been carried out will be noticed in a brief.

Description of Prominent Iron-Clad Vessels.  CLASS I. Classified with reference to the protection, the dimensions of the English Warrior and Black Prince are, length 380 feet, beam 58 feet, depth 33 feet, measurement 6,038 tons.  Their armor (previously described) extends from the upper deck down to 5 feet below water, throughout 200 feet of the length amidships.  Vertical shot-proof bulkheads joining the side armor form a box or casemate in the middle of the vessel, in which the 26 casemate-guns, mostly 68-pounder smooth-bores, are situated and fired through port-holes in the ordinary manner.  Their speed on trial is about 14 knots,—­at sea, about 12.  The Defence and Resistance, of 275 feet length and 3,668 tons, and carrying 14 casemate-guns, are similarly constructed, though their speed is slow.  All these vessels are built entirely of iron.