MARITIME CONVEYANCE. 



IN the present article we propose, first, to say a 

 few words as to the principles of naval archi- 

 tecture, to speak of practical shipbuilding in wood 

 and iron, and to describe the different classes ol 

 ships. We shall give a short history of steam- 

 propulsion, and some account of its present con- 

 dition, with an account also of the present condi- 

 tion of our merchant navy ; and, in conclusion, 

 we shall glance at some points connected with 

 navigation which may fairly come under the head 

 of Maritime Conveyance. 



Of the early history of ship-architecture little 

 can be said of any importance. The buoyant 

 property of water must have been early observed 

 by mankind ; and, beginning with rude skiffs and 

 canoes, they would in time acquire sufficient skill 

 and experience to build vessels of a larger size, 

 and to guide them in the required direction by 

 means of a rudder and sails. The cultivated 

 nations of antiquity Egyptians, Phoenicians, 

 Carthaginians, and others possessed ships for 

 commerce and war, some of which were of large 

 dimensions. Galleys, or vessels propelled by 

 oars, continued in common use till the sixteenth 

 century, and played a principal part in all sea- 

 fights up to that time ;* but of these early vessels, 

 as well as of those now employed by half-civilised 

 nations, it is unnecessary here to speak ; we pro- 

 ceed rather to notice the construction and char- 

 acter of ships as they are made now that naval 

 architecture has become a science. 



SHIPS. 



The naval architect and the shipbuilder stand 

 in the same relation to each other in reference to 

 ships as the architect and builder do in reference 

 to buildings, the one designing, and the other 

 executing. In most cases, however, the two pro- 

 fessions are combined in one firm, if not in the 

 same men. All ships have to possess certain 

 qualities, the principal of which are buoyancy, 

 stability, handiness, and speed ; but it is not pos- 

 sible for any ship to possess at the same time the 

 maximum of all these, as to some extent they 

 neutralise each other. The skill of the naval 

 architect is shewn in duly proportioning them to 

 one another, ascertaining which arc the more 

 important in each particular case, and providing 

 these without unduly impairing the others. In 

 some vessels, it is essential that the greatest pos- 

 sible speed should be attained ; while, as they are 

 to work only in smooth water, their degree of 

 stability (or freedom from excessive rolling, and 

 tendency to right themselves when heeled over by 

 a wave) is only secondary. In others, which have 

 to weather long-continued storms in mid-ocean, 

 speed may have to be sacrificed to attain greater 



* The first ship, properly so called, in the English navy was the 

 Great Harry, built in the reign of Henry VII. 



29 



steadiness. In sailing-vessels, where the means 

 of propulsion is not under control of the crew as 

 in steamers, handiness, the property of answering 

 quickly to their helms and of readily performing 

 various manoeuvres (such as tacking) under all 

 conditions of weather, is often the quality to which 

 most attention has to be paid. Along with all 

 these things, the ship has to be made so as to 

 have the largest possible amount of cargo or pas- 

 senger space consistent with the proper degree of 

 buoyancy. 



The degree in which a ship possesses the 

 various qualities named depends chiefly upon her 

 external form and dimensions, and about these 

 we must, therefore, say a little. The hull or body 

 of a ship is supposed to be divided into two parts, 

 called fore and after body, the one in front of, and 

 the other behind, the greatest breadth of the 

 vessel ; and the curves of the body are called its 

 'lines.' In a vessel required specially to carry 

 large cargo in proportion to her size, the lines will 

 be ' full ; ' and in one in which great speed has to 

 be attained at the expense of cargo-room, they 

 will be ' fine.' Whether full or fine, however, in 

 every well-designed ship they must be ' fair' that 

 is, continuous, and without any sudden changes 

 of direction or curvature. Next to the fairness of 

 the lines, the most important point about the design- 

 ing of a ship is the proper proportioning of the 

 lengths of the fore and after bodies. Our know- 

 ledge in these matters is quite recent, and we owe 

 it in great measure to Mr Scott Russell and the 

 late Professor Rankine. These gentlemen inves- 

 tigated scientifically the causes of the resistance 

 offered by water to a ship's motion, and arrived 

 at conclusions which are extremely valuable to 

 the naval architect, but mostly too abstruse to be 

 given here. Every vessel in moving through 

 water must raise at least two waves on the sur- 

 face, and cause them to travel along with her. As 

 long as these waves travel in a direction parallel 

 to that in which the ship moves, no appreciable 

 Dower is lost in keeping them in motion ; but if 

 :hey diverge obliquely from the ship's course, 

 they continually absorb power which ought to be 

 employed in propelling the ship. It was the object 

 of Mr Scott Russell's researches to find out how 



ship might be designed so that no power might 

 be thrown away in producing these oblique 

 waves. It is known that the length of a wave,* 

 like the length of a pendulum, determines the 

 velocity with which it will naturally move. Mr 

 Russell has shewn that the length of the fore and 

 after bodies of a ship should bear certain definite 

 proportions to the lengths of waves which would 

 naturally travel at a speed equal to the maximum 

 speed which the ship is intended to attain. For 

 every speed, therefore, there is a certain minimum 

 length which the vessel must possess. It may 

 often exceed this length with advantage, but can- 

 not fall short of it without inducing a waste of 



* Or distance from crest to crest 



449 



