STEAM NAVIGATION. 



as is possible, without altogether abandoning the principle of the split 

 paddle. 



59. The paddle-wheels generally used in American steam -boats are 

 formed, as if by the combination of two or more common paddle-wheels, 

 placed one outside the other, on the same axle, but so that the paddle- 

 boards of each may have an intermediate position between those of the 

 adjacent one, as represented in fig. 16. 



The spokes, which are bolted to cast-iron flanges, are of wood. These 



flanges, to which they are so 



- ]6 - bolted, are keyed upon the 



paddle-shaft. The outer ex- 

 tremities of the spokes are 

 attached to circular bands or 

 hoops of iron, surrounding 

 the wheel ; and the paddle- 

 boards, which are formed of 

 hard wood, are bolted to the 

 spokes. The wheels, thus 

 constructed, sometimes con- 

 sist of three, and not unfre- 

 quently four, independent cir- 

 cles of paddle-boards, placed 

 one beside the other, and so 

 adjusted in their position, 

 that the boards of no two 

 divisions shall correspond. 



The great magnitude of the 

 paddle-wheels, and the cir- 

 cumstance of the navigation 

 being carried on, for the most 

 part, in smooth water, have 

 rendered unnecessary, in Ame- 

 rica, the adoption of any of 



those expedients for neutralising the effects of the oblique action of the 

 paddles, which have been tried, but hitherto with so little success, in Europe. * 



60. The practical objections to the use of the feathering prin- 

 ciple in general, go far to balance the advantages attending them. 

 According to Mr. Bourne, whose skill and experience on this 

 subject entitle his opinion to the highest respect, all expedients 

 of this class are expensive, both to make and maintain. The 

 wear and friction in such a multitude of joints is very consider- 

 able ; and if any of the arms get adrift, or break, they will be 

 whirled round like a flail, and may perhaps cut through the 

 paddle-box, or even the vessel. If the injury be of such a nature 

 that the wheels cannot be turned round (and this has sometimes 

 happened), it will follow that the engines will be virtually dis- 

 abled until the obstruction can be cleared away; and if the 

 weather be very stormy, or the vessel be in a critical situation, 



* For a notice of the inland steam navigation of the United States, see 

 Railway Economy," chap. xvi. Also "Museum of Science and Art," 



vol. 11. p. 

 156 



17. 



