The self-discharge of water from a lifeboat is not so easy to explain. It will be the more readily comprehended if the reader understands, and will bear in remembrance, the physical fact that water will, and must, find its level. That is--no portion of water, small or great, in tub, pond, or sea, can for a moment remain above its flat and level surface, except when forced into motion, or commotion. Left to itself it infallibly flattens out, becomes calm, lies still in the lowest attainable position--in other words, finds its level. Bearing this in mind, let us look again at Figure 3. The dotted double line about the middle of the boat, extending from stem to stern, represents the _floor_ of the boat, on which the men's feet rest when standing or sitting in it. It also represents, or very nearly so, the waterline outside, that is, the depth to which the boat will sink when afloat, manned and loaded. Therefore, the _boat's floor_ and the _ocean_ _surface_ are on the same level. Observe that! The space between the floor and the keel is filled up with cork or other ballast. Now, there are six large holes in the boat's floor--each hole six inches in diameter--into which are fitted six metal tubes, which pass down by the side of the cork ballast, and right through the bottom of the boat itself; thus making six large openings into the sea. "But hallo!" you exclaim, "won't the water from below rush up through these holes and fill the boat?" It will indeed rush up into these holes, but it will not fill the boat because it will have found its level--the level of ocean--on reaching the floor. Well, besides having reached its level, the water in the tubes has reached six valves, which will open downwards to let water out, but which won't open upwards to let it in. Now, suppose a huge billow topples into the boat and fills it quite full, is it not obvious that all the water in the boat stands _above_ the ocean's level--being above the boat's floor? Like a wise element, it immediately seeks its own level by the only mode of egress--the discharging tubes; and when it has found its level, it has also found the floor of the boat. In other words, it is all gone! moreover, it rushes out so violently that a lifeboat, filled to overflowing, frees itself, as I have already said, in less than one minute!