740 



HISTORY OF THE SEA. 



mating so much more disturbance in the water. From that 

 time to this the English have followed the American models 

 m the construction and equipment of their steamers, and their 

 example has been imitated by most other nations. 



The latest specimens of American ship building are shown 

 in the cut representing the Pennsylvania and Ohio on the 

 stocks. These vessels are the pioneers of the new line between 

 Philadelphia and Liverpool. 



Nor is this the only change which naval architecture has 

 undergone. The material for ship-building, especially for sea 

 going steamers, has in modern times come to be chiefly iron. 

 Livingstone, in his book of travels in Africa, tells how, when 

 he was putting together on the banks of one of the rivers 

 there the pieces of a small iron steamer which had been sent 

 out to him from England, the natives gathered round, and in- 

 specting the work going on, jeered at him for thinking that 

 a boat built of such a material would float. Their whole ex- 

 perience with iron was that it would sink. When, however, 

 the steamer was completed and launched, they could hardly 

 express their astonishment at finding that she floated. 



Though evory school-boy, from his text-books on natura. 

 philosophy, can explain the reasons why a ship bviH of iron 

 will float, yet our ancestors would have considered a proposi 

 tion to construct a ship from this material very n\uch as the 

 native Africans did. Even in the construction of wooden 

 ships, iron enters now much more than it did formerly. The 

 knees, or bent oak beams, by which the form of the ship was 

 made, have become so scarce and dear that they are now fre 

 quently made of iron. It takes so long for an oak tree to 

 grow, and the demand was so great for limbs of such a natura] 

 bend as could be used for ship-building, that even before the 

 use of iron for such portions of a ship, the process was in fre- 

 quent use of bending the beams, or knees, by steaming them 

 *nd then objecting them to great pressure. 



