The object of this construction is to combine, as far as possible, all the advantages of the wooden and the iron ship. There are three main systems of English types ranging from a close approximation to the wooden construction to that of the iron sheathed with wood, which latter forms the connection between composite and iron construction. In McLain’s system, which is the closest approximation to the wood construction, the keel, stem and stern posts, frame, and outer planking are of wood. The ceiling or inner planking, however, is of iron, forming a complete iron inner skin; the beams, knees, stringers, keelsons, transoms, and breast-hooks being also of iron. The wooden frames are of a smaller scantling than in the wooden system, being supplemented by angle-iron frames, by means of which the iron skin is secured to them. The outer planking bolts directly to the wooden frames, being kept entirely clear of the iron inner hull. In Jordan’s system the frames are entirely of iron, inner and outer skins being of wood, whilst the keelsons, stringers, and transverse supports are of iron. In Scott’s system the frames are made of T-iron instead of angle-iron as in Jordan’s system, and a modification is introduced by which the frames are spaced much farther apart. Between the frames oak or teak chocks are fitted, bolted to the frames and calked throughout, thus forming a complete water-tight course. These are the main types as represented in England. In Russia is found another system which, doing away with diagonal braces, which it must be remembered are used with all the systems just described, makes use of the McLain system in connection with Mr. Scott Russell’s method of longitudinal strengthening. In this, the keel, stem and stern posts, and outer planking are of wood, whilst the frame is of iron with an iron skin outside of it, which in general terms would class the type with that of iron ships sheathed with wood. To the outside of this iron skin Z-iron stringers are bolted, the space between them being filled up by chocks to form a complete wooden sheathing. These chocks are made shorter than the spaces, and are wedged in their seats. Outside of this sheathing is run the wooden outer planking in the ordinary way. It will be seen by the descriptions following that this system can scarcely be classed as a true composite. [Illustration: Scott’s Composite Construction.] [Illustration: McLain’s Composite Construction.] [Illustration: Russian System.] [Illustration: French Gun-boat Crocodile. (Composite.)] [Illustration: French Transport Annamite. (Composite.)]