220 



HYDRAULICS. 



height, so as not to incommode the passengers. 

 The vessel is directed in the usual manner by a 

 rudder. 



Some attempts have been made to place the 

 water wheels, or paddles that drive the vessel, in 

 the middle, instead of being on the sides, by which 

 construction the steam vessel appears double, with 

 the wheels between : and this idea promises some 

 advantages. On the first employment of the 

 steam engine for this purpose, several accidents 

 happened from the bursting of the boilers, which 

 were of cast iron. But since the boilers have been 

 made of wrought iron, this danger is very much 

 lessened; and it would appear that steam vessels 

 are now quite as safe as any other mode of con- 

 veyance. The chief advantages is the certainty 

 of the conveyance, as they do not depend upon 

 wind or tide. 



