Iron is now employed in almost every part of a war-ship, the masts themselves being in many cases of iron--hollow tubes through which the running rigging may be let down when there is danger of its being damaged by the enemy's fire. The majority of modern ironclads are built in compartments, with this advantage that, if damage is sustained in one part of the vessel, and the water rush in through the gap made by shot or any other cause, the ship will still float until the water can be let out again. The American ironclad turret-ship _Monitor_ has given her name to a whole class of vessels built within recent years for the English navy; but in many respects our vessels are superior to their American prototype. All these ships--which are characterised by low free-boards and absence of masts and sails--fight their guns from turrets. They are sometimes known as "coast-defence ships," from the circumstance that they were constructed mainly for home service. Of these "English monitors," four--the _Cyclops_, _Gorgon_, _Hecate_, and _Hydra_--are built on identically similar principles. In appearance they may be best compared to a raft with a battery on top of it, from which fortress or battery rise various funnels and a flag-staff. The deck is but three feet and a half above the level of the sea. While the ships are in port the deck is roofed in with an awning and railed round; but both awning and railing are removed when the vessels put to sea. The battery or fortress is in the centre of the ship, and fills up about one-third of her length and three-fourths of her breadth. The surrounding deck is flush, its surface being broken only by the skylights, which are three in number. The skylights allow but a scant and dim light to penetrate to the officers' and seamen's quarters below; but even this is wanting in time of action, when a shot-proof shield takes the place of the glass windows. The deck of the dass of war-ships we are describing is composed of twin-layers of iron plating half an inch each in thickness, supported on iron beams, and of two layers of solid teak lining four inches thick. The sides of the ships are protected by iron plating of eight-inch thickness amidships, which is an inch more of iron than the armour possessed by the majority of our masted sea-going ironclads, many of which are twice or thrice the size of the _Cyclops_ and her sister-ships. It will thus be seen that these turret-ships are practically stronger in defensive equipment than any other class of ironclad cruisers.