In examining and discussing different systems of construction it is necessary to always keep in mind the great distinctions between composite, iron, and iron sheathed with wood. Those who cry down the wooden construction, in view of the rapid deterioration of the American unarmored fleet, must bear in mind that this fleet was constructed of the worst possible material. In discussing the advantages of the composite system, those of the diagonal system must not be lost sight of. Above all, it must be remembered that the disadvantages of the pure iron construction, as evidenced by English and French target experiments, have never been overcome. The iron and steel sheathed with wood is an amelioration, but as yet it is by no means a satisfactory one. Although England has totally discarded the wood construction, it must be remembered that France holds her own with but a partial introduction of iron and composite in her highest and lowest rates. The subject of constructional development is still in its experimental stage, and to those nations who, unlike Great Britain, cannot depend upon legislative support and sympathy, nothing is more dangerous to the healthy development of an efficient unarmored fleet than a hasty adoption of a new constructional type. ARMORED VESSELS. ARCHITECTURAL DEVELOPMENT. It would be useless to attempt to assemble in chronological order the many propositions that have been submitted to or even entertained by different maritime governments looking towards the building of armored vessels. The first serious attempt made and effectually carried out was by France in 1855, when there were built five floating batteries carrying an armor of five inches, which, although almost totally unmanageable from their bad lines and realizing a speed of but four knots, went into action on the 17th of October in that year and silenced the batteries of Kinburn. These vessels taught nothing with regard to architectural development, but at the instance of France the English Government built nearly at the same time some vessels quite similar, and the attention which this movement caused led to a consideration of the suggestions of Captain Coles, who, in the same year, sent into action the little cupola vessel Lady Nancy. Had it not been for the dire necessity for an armored vessel to hold the Merrimac in check, Ericsson would not have won for the United States the credit of introducing the monitor type of vessel. Whilst he was designing the lines and arrangements of the Monitor, Coles was engaged in almost precisely the same work for the Danish Government, designing the Rolf Krake.