A boat built like the half of a split porcupine's quill could enter the water with the least resistance, but would leave it with the greatest; in fact, she would not travel at all, because her bluff stern would create a sudden vacuum behind her, which would retard her progress. This is a _reductio ad absurdum_, but it shows the effect of having the greatest beam too far aft. The problem to be solved in designing the lines of a boat is so to arrange her entry into the water, that what she displaces in front may with greatest ease flow aft to fill the vacuum aft which she leaves as she progresses. Otherwise she pushes a heavy wave in front of her, and drags another behind her. If anyone will watch the bank as a racing eight passes, noting the level of the water at a rathole, he will see the level of the stream first rise as the boat comes nearly abreast of his point of observation. Then, as she passes, the water will sink, and after she has passed it will rise again higher than before she neared the spot. The first rise is caused by the boat pushing a wave in front of her: the following depression is caused by the vacuum which she is leaving behind her, and the final rise by the wave which runs behind her to fill her vacuum. Obviously, the less water the vessel moves the easier she travels. If by any designing the wave pushed in front could be induced to run more or less back to the stern, then the second (following) wave would be more or less reduced in bulk, and the labour would be proportionately lighter. The finer the lines taper aft, the easier the front wave displaced finds its way to the vacuum aft. _Per contra_, the more bluff the midship and stern sections, the greater the difficulty in filling the vacuum aft. Builders hamper themselves by adhering to a red-tape idea that all oarsmen in a boat should be seated at equal distances from each other. So long as designers adhere to this, they require a good deal of beam aft, if Nos. 6, 7 and stroke are of anything like average size. Of course, there must be a minimum of space for each man to reach out in; but there is no reason why in some of the seats the space should not exceed this minimum, e.g. to set the first four men at the minimum, and then to place No. 5 and extra inch past No. 4 and so on, with perhaps stroke and 7 1-1/2 inches further apart than the forward men, would enable the builder to attain a greater longitudinal displacement at the sternmost part of the boat than he would otherwise require to carry his men. In lieu of this gain, he can then reduce his beam and depth aft, and so make his lines taper more to the stern.