The rowing process, whether illustrated by the leathern tub-like coracle of the Cwmry, or the fish-like, skin-covered frame of the Esquimaux, or the birch-bark canoe of the Red Indian proper, or the war-galleys of the Greeks and Romans, or those of the Crusades, or the war-canoes of the New Zealanders in Cook’s time, or the Malay Proas of past and present, was a result in some cases of want of skill or materials, or both, to build or work craft that would stand up under sail, and in others the necessity of substituting a certain for an uncertain power, though at the cost of heavy labour. In all sea-fights skilful sailors working by the aid of the wind endeavoured to obtain the “weather gage,” i.e., the power of attacking their opponent from the windward side, and so choosing their point of attack. But in a calm it is obvious that a galley without oars would be at the mercy of a row-galley, as to the insertion of the beak, in the absence of heavy projectiles. So also in a calm, a small steam vessel with heavy guns would rake and destroy almost unresistingly the heaviest wood-built craft afloat, depending wholly on the wind, though with a very small auxiliary steam power the heavy craft could contrive to turn on her heel, and, like a Spanish bull, keep her front to the enemy, even though reduced to the extremity of feeding her boiler with her own sails, rigging, and bulkheads, in default of coal; and, unless the swordfish of a steamer had the longest metal, the whale of a wooden craft would keep the swordfish at a distance.
Oars were the first rowers, but the inventor of artillery rendered them liable to a raking shot which would sweep the side clean, and disable all the oarsmen; so they were abolished, save under the name of “sweeps” for very occasional use. The inconvenience of the oars by their great leverage on the vessel’s side very early gave rise to trials of side paddles moved by animal power, as is still the case on American ferries, where a yoke of oxen are made to climb up an inclined wheel connected by gearing with the paddle-shaft. And if we may credit the archives of Simancas in Spain, one Blasco de Gomez, a Spanish engineer, did, in times long past, substitute for the oxen a better or worse kind of steam engine with which he propelled a vessel round the harbour of Barcelona, in the presence of the Emperor Charles, by means of paddle-wheels. He was simply before his time.
The advantage of oars as best used, over paddles, as commonly used, is that the oar is turned edgewise on entering and leaving the water, thus avoiding the waste of power. An ordinary paddle wastes power on leaving the water by lifting a weight of water, and tending to force down the boat, increasing the friction on the shaft; to meet this difficulty paddles are made to feather mechanically, similarly to the oars, but this involves more costly machinery in a position exposed to much wear.
Both oars and paddles are inconvenient projections from a vessel’s side. Moreover, the paddles have the inconvenience in a heavy sea of being sometimes only immersed on one side, giving rise to numerous disadvantages. For this reason the steam-screw was introduced, being more out of the way and wholly immersed in the sea, unless in very heavy pitching.
In the use of the paddles the vessel is propelled by the steam power exerted through the horizontal shaft on the fulcrum of the bearings. To keep these bearings from heating under the friction of the enormous pressure, it is essential to preserve a cushion of oil between the metallic surfaces. If the area of the surfaces be too small the oil will squeeze out, and contact of the metals will ensue; or if the surface be rough, salient points will come in contact, and then heating will ensue. The area of bearing which is sufficient to prevent a shaft from breaking or from heating in smooth water, is not sufficient in heavy seas, for positive blows ensue. For example, one paddle is out of the water and revolving at extra speed, when suddenly the water rises perchance with the engines at full stroke, and a shock ensues, causing the whole vessel to tremble, and possibly breaking the shaft or stripping off the paddles.
The stern screw is less exposed to this kind of blow, but it has nevertheless its difficulties to contend with. It propels the vessel by pressing a pair of metal rungs, forming an inclined plane, against the stern water at one end of the shaft, and pressing with the other end of the shaft or with collars against a bearing, inside of the vessel. As the shaft revolves, the screw, or inclined plane, cuts off a continual slice of the water in front, and pushes it behind as a fresh fulcrum, by which operation the vessel continally advances. But as the end of the screw, or the collars, inside the vessel are continually revolving, while thrusting the vessel forward, it requires a larger area, and continual ample lubrication to prevent heating.
There is yet more. The shaft must be guided vertically and horizontally in bearings at certain intervals to prevent it from breaking, and where it issues from the vessel, the leverage of the screw against the water causes it to tremble and vibrate enormously, just where the vessel is weakest; and in wooden vessels converted to screw propulsion the difficulty and cost of repairs are very great. It is found that metal linings for the screw shaft are quite inefficient, and surfaces of wood are required. If any lever movement obtains in the screw shaft, the destruction of the bearings is very rapid.
In both screws and paddles there appears to be a defective arrangement, from ignoring one portion of the data required to be started from. Workmanship has attained so high a point of excellence, that engineers deem rigidity perfectly compatible with durability, forgetting that Nature knows no absolute exactitude, and provides for irregularity by the great compensating principle of elasticity, as in the waving boughs of trees, and the spiral springs wherewith she hangs grape vines to walls and branches, and as the tendons of a horse’s pasterns which save his feet from becoming a mere hammer, or as a man jumping on his toes sustains no harm, but is seriously shaken by alighting on his heels.
As constructed, paddles and screws have heels and no toes, though the paddles are analogous to the side fins of a fish, which are a mass of springs, and, moreover the latter are always immersed, and get no blows. Now there would be no difficulty in