Each successive year new vessels have been built, surpassing their predecessors in their size and power and in the splendour of their decorations, while they possess every improvement the skill, taste, and experience of their constructor can devise. There exists, nevertheless, in the general external appearance of the boats employed on the river navigation a great similarity which may be seen also in the details of their construction and in that of their machinery, as well as to some extent in their models, their usual features being great proportion of length to beam, a shallow hold, and a long flat floor, extending almost to the extremities of the boat. Great buoyancy, and consequently, a very light draught of water are by these means secured, and as the shallowness of the rivers in some places requires this, experience has demonstrated the advantage of attempting to go over rather than through the water when it is desirable to attain very high speed. Although the absolutely best form of model and that which, under all circumstances, is subject to the least average resistance remains a matter of speculation, every builder having an opinion and theory of his own differing more or less from those entertained by his brethren of the craft, the competition and rivalry between the different builders and owners have been productive of extraordinary results. On the American rivers a sustained average speed of 20 miles per hour is now not an uncommon performance, due, doubtless, in part, to the improved form and fineness of the water lines, and, in part, also, to the great size and power of recent engines: add to this, that, from the superior tenacity and strength of American iron, the constructor is able to give his engines proportions considerably lighter than would be deemed safe elsewhere. The immense diameter of their paddle-wheels is also worthy of note as an element of no mean importance in the economical expenditure of the power developed in the engine and, consequently, in its effect on the speed of the boat. Taken as a whole, therefore, it would be impossible to find anywhere else finer specimens of naval architecture or more suitable engines for the special traffic on which they are engaged, than the boats now traversing the coasts, rivers, and lakes of the United States. [Illustration: HUDSON RIVER STEAMER “NEW WORLD.”]