SPLIT PADDLES. 



but is still acute ; at G it increases to a right angle ; at H it becomes 

 obtuse ; and at K, where it is most distant from the centre p, it becomes 

 most obtuse. It again diminishes at L, and becomes a right angle between 

 A and B. Now this continual shifting of the direction of the short arm K 

 is necessarily accompanied by an equivalent change of position in the 

 paddle-board to which it is attached ; and the position of the second centre 

 p is, or may be, so adjusted that this paddle-board, as it enters the water 

 and emerges from it, shall be such as shall be most advantageous for pro- 

 pelling the vessel, and therefore attended with less of that vibration which 

 arises chiefly from the alternate depression and elevation of the water, 

 owing to the oblique action of the paddle -boards. 



58. Field's split paddles. In the year 1833, Mr. Field, of the firm of 

 Maudslay and Field, constructed a paddle-wheel with fixed paddle-boards, 

 but each board being divided into several narrow slips arranged one a little 

 behind the other, as represented in fig. 15. These divided boards he pro- 

 Fig. 15. 



posed to arrange in such cycloidal curves that they must all enter the 

 water at the same place in immediate succession, avoiding the shock pro- 

 duced by the entrance of the common board. These split paddle-boai'ds 

 are as efficient in propelling when at the lowest point as the common 

 paddle -boards, and, when they emerge, the water escapes simultaneously 

 from each narrow board, and is not thrown up, as is the case with common 

 paddle-boards. 



The /number of bars, or separate parts into which each paddle-board is 

 divided, has been very various. When first introduced, each board was 

 divided into six or seven parts : this was subsequently reduced ; and in 

 the wheels of this form constructed for the government vessels, the paddle- 

 boards consist only of two parts, coming as near to the common wheel 



155 



