The _planks_ follow the ribs. These are broad, and vary in thickness from two to four inches. They form the outer skin of the ship, and are fastened to the ribs, keel, stem-post, and stern-post by means of innumerable pins of wood or iron, called _tree-nails_. The spaces between the planks are caulked--that is, _stuffed_ with oakum; which substance is simply the untwisted tow of old and tarry ropes. A figure-head of some ornamental kind having been placed on the top and front of the stem-post, just above the cutwater, and a flat, ornamental stern, with windows in it to light the cabin, the hull of our ship is complete. But the interior arrangements have yet to be described, although, of course, they have been progressing at the same time with the rest. The _beams_ of a ship are massive wooden timbers, which extend across from side to side in a series of tiers. They serve the purpose of binding the sides together, of preventing them from collapsing, and of supporting the decks, as well as of giving compactness and great strength to the whole structure. The _decks_ are simply plank floors nailed to the beams, and serve very much the same purposes as the floors of a house. They also help to strengthen the ship longitudinally. All ships have at least one complete deck; most have two, with a half-deck at the stern, called the _quarter-deck_, and another at the bow, called the _forecastle_. But the decks of large ships are still more numerous. Those of a first-rate man-of-war are as follows--we begin with the lowest, which is considerably under the surface of the sea:-- The Orlop-deck, the Gun-deck, the Middle-deck, the Upper-deck, the Quarter-deck, and the Poop--the latter deck being the highest deck of all, a very small one, at the stern. Thus a man-of-war is a floating house with six stories--the poop being the garret, and the orlop-deck the cellars. The upper decks are lighted by sky-lights; those farther down by port-holes (or gun-holes) and windows; the lowest of all by candles or lamps, daylight being for ever banished from those gloomy submarine regions! The _bulwarks_ rise above the upper-deck, all round the ship, and serve the purposes of protecting the upper-deck from the waves, and supporting the _belaying-pins_, to which the ropes are fastened. In ships of war the top of the bulwarks forms a sort of trough all round the ship, in which the hammocks (the swinging-beds) of the men are stowed away every morning. This trough is termed the _hammock-nettings_, and the hammocks are placed there to be well aired. In action the bulwarks serve to protect the crew from musketry. The _wheel_, which has been already referred to, stands usually at the stern of the ship, on the quarter-deck; but it is sometimes placed on an elevated platform amid-ships, so that the steersman may see more clearly where he is going.