These ships were followed by a series of rigged ships of the writer’s design, _viz._, the _Bellerophon_, _Hercules_, _Sultan_, _Penelope_, _Invincible_, _Iron Duke_, _Vanguard_, _Swiftsure_, and _Triumph_, all with hulls of iron, or of iron and steel combined, together with a series of rigged ships constructed of wood, converted from unarmored hulls or frames, _viz._, _Enterprise_, _Research_, _Favorite_, _Pallas_, _Lord Warden_, _Lord Clyde_, and _Repulse_. Every one of these ships was protected by armor throughout the entire length of the vessel in the region of the water-line, and in some cases the armor rose up to the upper deck. Most of them, however, had the armor above the belt limited to a central battery. The chief interest in these vessels now lies in the illustrations they furnish of the evolution, so to speak, of bow and stern fire. In several of them a fire approximately ahead and astern (reaching to those directions within about twenty degrees) was obtained by means of ports cut near to the ship’s side, through the transverse armored bulkheads. In others these bulkheads were turned inward towards the battery near the sides of the ship in order to facilitate the working of the guns when firing as nearly ahead and astern as was practicable. In the _Sultan_ an upper-deck armored battery was adopted for the double purpose of forming a redoubt from which the ship could be manœuvred and fought in action, and of providing a direct stern fire from protected guns. In the five ships of the _Invincible_ class a direct head and stern fire was obtained from a somewhat similar upper-deck battery, which projected a few feet beyond the side of the ship. [Illustration: THE “SULTAN.”]