the utmost importance. Thus, it is in the case of ships and forts alone that the problem and means of defence become equally essential with those of offence; and that the former, like the latter, are of a highly definite and special character, and only to be advanced through careful study of the mechanical and other conditions involved. In fact, in the case of ships, it is most distinctly seen to be true that, when the defence can no longer be improved so as reasonably to keep pace with increasing efficiency and power in the means of assault, the necessary alternative must be the abandonment altogether of naval warfare, or the comparative worthlessness, at the least, of any resort to it. Now, since the early part of the present century, a steady increase has been going forward in the caliber of ordnance and in its available power, that is, in other words, in the penetrative and, generally, the destructive effect of projectiles; while the course and prospects of a naval engagement have been, in a particular manner, changed by the introduction of the so-called Paixhan guns, which throw shells of great weight and at a velocity sufficient for penetrating the wooden sides of the ordinary ships of war, preparatory to spreading destruction and conflagration within them. It is these facts that have forced upon military authorities of the time the specific problem of defence, especially for all classes of war vessels, and so urgently that within the past three years it has become the paramount question in connection with the practice of warfare. Under such circumstances, the subject can, of course, only be presented as one in a state of progress-its results being not merely still undecided, but for the present beyond even the reach of conjecture.

The Necessity of Armor Recognized.-A ship or boat, then, being a definite point or object of attack, and the penetration and destructiveness of solid and hollow shot having been gradually and very greatly increased, the inevitable consequence was that, sooner or later, wooden war vessels must become too vulnerable to leave even a reasonable chance of their withstanding a well-directed fire. And, this point once reached, the idea of seeking a more efficient resisting material in some metal, and naturally in iron, must, by a necessity just as inevitable, have presented itself; so that it becomes a matter of slight importance at what precise time, or by whom, the suggestion of such a change was publicly made. By some authorities the proposition is accredited to Mr. John Stevens, of New Jersey, its date about the year 1811; by others, to Col. Paixhan, of the English army, some ten years later.

Among the earliest systematic experiments with a view to the substitution of the resistance of iron for that of wood in the sides of ships, were those made by English authorities in the year 1840, and a few years following, in the way of firing upon targets representing a portion of the side of an iron ship, as ordina

rily constructed. As a result, it was found that the thin plates of such ships, when struck by projectiles that pierced them, crushed into fragments, which were scattered with peculiarly destructive effect; so that ordinary iron ships were wholly unsuitable for war purposes. A definite proposal for constructing shot-proof iron floating batteries was, about the year 1852, entertained by the United States Government; but the results of experiments made with a view to that end being deemed unfavorable, the project was, for the time, abandoned. Still, the subject was more or less under discussion in this country, and in France and England. It is said that, many years previously, an imperfect attempt had been made at mailing the English ships which took part in the battle of Algesiras (1801), and that, subsequently to that occasion, M. Montgéry, of France, had published several memoirs on the subject. The project having become, in that country, in a degree forgotten, attention was again called to it during the war between France and Russia, by the circumstance that wooden ships were found incapable of withstanding a skilfully-directed fire from near land batteries. The French emperor directed, in 1854, that experiments should be made with a view to the protection by iron armor of ships of a draught rendering them suitable to be employed in an attack on Cronstadt. Upon a renewal of some experiments discontinued about 15 years before, the conclusion was reached that, in order to afford protection against the round shot then in actual use, a thickness of mètre = 3.937 inches, was required. Of the armored boats or floating batteries hastily constructed in accordance with these views, and which, from the weight of the plates and the depth of water they drew, were incapable of speed, and even of independent navigation, three that were taken to the French fleet, then before Kinburn, participated in the attack, Oct. 1855, on the forts at that place. Though struck by very many 24-lb. balls at about 600 yards, the armor of these boats was not actually pierced, but only somewhat deeply indented; but considerable injury was done by shots which entered the portholes. Some British batteries of like construction did not arrive so as to take part in the action.

In the year 1854, experiments in relation to iron armor were also made in England; in these, a target, consisting of a wood backing covered with wrought-iron plates of 4 inches thickness, and intended to represent the side of an armored ship, was found to be indented at 400 yards by 32-lb. solid shot and 8-inch and 10-inch hollow shot, to depths respectively of 11, 1, and 2 inches; while 68-lb. solid shot, fired with 16 lbs. of powder, penetrated the plates, splitting them especially in the line of the bolt-holes, which were about 1 foot asunder. In France, a new interest was awakened, by the comparative success of its trial at

Kinburn, in the subject of iron armor; and, in experiments in which 50-lb. balls were fired at several yards' distance, and with a heavy charge of powder, upon plates of the thickness already adopted, it was found that the balls sufficed to break the plates, though they did not go through them. The results, however, differed much with differences in quality of the iron; and, if not previously admitted, it now became evident that, for resistance to shot, a somewhat soft iron is preferable to an iron having great hardness, with its attendant brittleness. The experiments undertaken in the United States had tended to show that, for guns of the largest caliber then in use, although 4inch plates, well backed with solid timber, were likely, for a time, to resist piercing by shot thrown from considerable distances, yet nothing less than 6 inches of iron plating could be relied on to render a ship practically invulnerable. This result was discouraging, in view of the fact that the complete armoring of a ship with 6-inch plates appeared to involve a weight which no vessel can carry without great sacrifice of speed, and a loss even of capacity for open-sea service.

The next step in the construction of iron-clad ships (French, vaisseaux en cuirass, or navires cuirassés), was the building of La Gloire in France (1860), and of the Warrior in England (1861). The armor of these ships is described in the preceding volume of this CYCLOPEDIA. Sir Howard Douglas has lately asserted in substance that both these ships are failures, so far as sea-going qualities, speed, and the stability requisite for successful firing upon a heavy sea, are concerned. Both appear to be, with combined armament and armor, overloaded, and owing to the lowering, in consequence, of the meta-centre (centre of pressure of the liquid displaced) to near the place of the centre of gravity, both these ships roll in a heavy sea with quick and considerable movements, so that the gunner's aim in such cases becomes extremely uncertain. Moreover, while La Gloire has not exceeded 11, in place of the 133 knots an hour anticipated, and the Warrior at sea not more than 12, the latter can carry but 9 days' coal, and in long voyages must often rely on tenders or sails. Apparently, therefore, these ships, and, probably, the others armored by the two nations upon respectively the same patterns, are not, on the score of their capacity for distant expeditions and aggressive warfare, very greatly to be dreaded.

The Revolving Turret, or Cupola.-But while ships may possibly be so armored as to be in the main nearly impregnable to an enemy's fire, yet their portholes remain subject to the entrance of shot, and that in proportion to the size that must be allowed for properly working and pointing the guns; while the lateral sweep in this way secured is always limited, and the entire ship must often be manoeuvred in order to bring the guns into the desired line. If, however, instead of the ordinary casemate

or broadside arrangement, the guns can be placed within a protecting structure which can be revolved into any required line of fire, sil the difficulties connected with the management of the guns, the exposure incident, and the continual effectiveness of the ship's armament, vIRish or are reduced to their minimum. such is the idea of the revolving turret or cupola, and such the objects to be attained through its use. The original invention of this important addition of the last few years to the means of naval warfare, has already been claimed on behalf of three persons, Capt. John Ericsson of New York city, Mr. Theodore R. Timby, of the State of New York, and Capt. Coles, of the British navy. In the year 1854, Capt. Erics son forwarded from New York to the emperre Napoleon a communication (dated Sept. 26) in reference to a new form of armored vesel for naval attack, designed by him-the plan embodying many of the features of the Monitor," presently to be referred to, but especially those of a deck rising but a few inches out of water, and of a turret amidships to contain ons or two large pieces of ordnance, and to be es pable of being revolved so as to bring the gas into any desired line of fire: the shape of tas turret, however, was that of a dome, or Lafa hollow globe, the ports being at one side. T. receipt of the communication was duly ac knowledged by the emperor. Capt. ESon further states that the idea of a revolving tower for ordnance upon land is very old - tet that the thought of placing such a structure upon a ship was original with himself, having been conceived many years before the time of the communication above mentioned. C Coles, in a letter to the (London)" Times" April 5, 1862, states that the idea of bulung impregnable vessels was suggested to him y his experience in the Baltic and Black seas in 1855, and that toward the close of that year be had a model for such vessels made, in wh-à he proposed to protect the guns by a stationary "shield" or "cupola." Notwithstanding cial neglect, he persevered, producing in Mar 1859, drawings of a "shield fitted with t tables;" and in December, 1860, he pubist an account, with drawings, in which the 14 form of the shield was to be turned by ma power. Mr. Timby constructed, in 184 model of a revolving tower for land fort's tions, pierced with one or two tiers of partholes, and to contain several guns, these ty fired in succession as they were brought by the revolution in line with the object of attack. A larger model was exhibited in many play a 1843, among others in New York, notices of 1 appearing in the "Evening Post" of Jus¦ of that year, and in the "Herald," during the same month. It will be seen that the poses and principle, on the one hand, if the Ericsson and Coles turrets (accounts of which will be given farther on), and on the other t that of Mr. Timby, are wholly distinct: wa the former, the revolution of the tower is at

the object sought, only so far as needful to point the guns upon the enemy; in the latter, the revolution is indispensable, as well as nearly continuous-a condition that must involve important difficulties in practice. So long as it revolves properly, the Ericsson turret serves to keep an enemy continually under fire, in spite of changes of position. In this way, two guns become-supposing no necessity of delay from their heating equal in effective force to at least eight mounted on stationary carriages.

Earliest American Iron-clad Vessels.-"It so happens," Admiral J. A. Dahlgren very appo sitely remarks in his Report supplementary to the Report of the Secretary of the Navy, Nov. 22, 1862, "that circumstances impose on England and France the necessity of grappling with the most difficult solution of the problem [that of armoring ships], their shores being washed by the deep waters of the ocean; therefore their iron clads must be more than mere floating batteries, and be possessed of the best nautical qualities. With the United States the case is, happily, different-the depth of water on the coast being generally adapted to vessels of light or moderate draught, and only a few of our ports being at all accessible to heavy iron clads like those of France and England. The solution of the question is, therefore, in its immediate requirements, comparatively easy and inexpensive for us. Vessels of the Monitor and Ironsides class are likely to serve present purposes sufficiently well, and to give time to obtain, from our own and the experience of others, better data than can now be had for advancing to a more perfect order of vessels." The facts here stated in respect to the general character of the coast navigation, Atlantic and Gulf, of this country, as also the great extent to which naval operations may require to be carried on in navigable sounds, bays, and rivers, but which are not always of great depth, have been kept in view in all the earlier attempts here made in the way of armoring vessels-with the single exception, indeed, of the first of them all, the Stevens Battery, the proposed draught of which is 21 feet. (For a full description of this bat tery, as well as of Capt. Ericsson's first iron-clad battery, the Monitor, the plan of which was one of the three first adopted by the United States Government, in 1861, see the preceding volume of the CYCLOPÆDIA.) Of these three patterns of iron-clad vessels, and the draught of which ranged from 10 to 13 feet, all were in fact mainly new in conception, differing from the earlier French and English batteries in being intended to realize independent navigation and fair speed, and from the Gloire and Warrior styles in being of much less dimensions, while also nearly or quite completely mailed. The most original in principle of the three, and the one that has come to be regarded as peculiarly the American style of iron-clad vessel, was the Monitor-a name that is now employed as distinctive of the growing class of vessels involv

ing the same general construction. The Monitor was built at the Continental Works, Greenpoint, L. I., by Mr. J. F. Rowland, under the direct supervision of Capt. Ericsson, and delivered to the Government, March 5, 1862. The vessels completed in accordance with the other two of the three contracts, were, for that with the firm of Merrick & Sons, Philadelphia, the New Ironsides, and for that with S. C. Bushnell and Co., of New Haven, Conn., the Galena.

The experiments preceding the inception of the Monitor had already determined that, since very hard and brittle plates are proportionally more liable to crack, and very soft ones to be simply punched or penetrated, for armoring in the modes thus far adopted, neither steel or hard cast iron on the one hand, nor copper or the softest wrought iron, on the other, should be employed, but in fact an iron possessing fair forging and rolling qualities, and having along with moderate hardness also a high degree of absolute strength or tenacity. In the case, however, of armor applied, not in a single thickness or plate, but in a succession of thinner plates (laminated armor), a harder iron or steel is said to be used with advantage. It will be remembered that the armor of the upper hull of the Monitor consisted of 5 inches of rolled iron (1-inch) plates; that of the turret generally of 9, and that of the deck of 2 inches of similar plating. Of course, though in England there is an apparently open avowal and discussion of all information acquired in respect to penetration of projectiles and qualities of armor indicated, it is probably true that in all the leading countries now interested in this question, as is evident in the case of the Government of the United States, there is nevertheless a degree of reticence in respect to important results, and especially as to certain points in the construction, armament, and working of iron-clad vessels. Hence, there are portions of information in regard to these subjects which can only become public after the lapse of a few years, or under a condition of national questions different from that which now exists. An account of the experiments in the way of testing the relative capacities of the most recent and improved ordnance and iron armor, with the bearing of the results on the questions of thickness, kind, quality, and extent of armor protection for vessels, as well as of the modes in which the plates are prepared for being applied, will be given farther

on.

The First Class Monitors (Smallest Size).— The course and result of the engagement between the Monitor and Merrimac, in Hampton Roads, March 9, 1862, having established the suitableness and success of the Ericsson form of battery, both for purposes of defence (at least, against guns of the power there employed) and of attack, orders were speedily issued by the U. S. Government for the construction of 10 similar batteries, one or more of which, indeed, must have been at the time already com