FEATHERING PADDLES. 



structure of the vessel, and with its depth of immersion ; never- 

 theless it is upon this proportion that the manner in which the 

 paddle-boards should shift their position must he determined. If 

 the progressive speed of the vessel were nearly equal to the rotative 

 speed of the paddle-boards, the latter should so shift their position 

 that their upper edges should be presented to a point very little 

 above the highest point of the wheel. This is a state of things 

 which could only take place in the case of a steamer of a small 

 draught of water, shallop-shaped, and so constructed as to suffer 

 little resistance from, the fluid. On the other hand, the greater 

 the depth of immersion, and the less fine the lines of the vessel, 

 the greater will be the resistance in passing through the water, 

 and the greater will be the proportion which the rotative speed of 

 the paddle-boards will bear to the progressive speed of the vessel. 

 In this latter case the independent motion of the paddle-boards 

 should be such that their edges, while in the water, shall be pre- 

 sented towards a point considerably above the highest point of the 

 paddle-wheel. 



A vast number of ingenious mechanical contrivances have been 

 invented and patented, for accomplishing the objects just explained. 

 Some of these have failed from the circumstance of their inventors 

 not clearly understanding what precise motion it was necessary to 

 impart to the paddle-boards ; others have failed from the com- 

 plexity of the mechanism by which the desired effect was produced. 



57. One of these contrivances of late construction is represented in 

 fig. 11, being the paddle-wheel of the Russian steamer "Peterhoff." 

 To convey a general idea of the feathering principle, however, we 

 have represented in fig. 14 the form of wheel known as Morgan's 

 paddle-wheel. 



This contrivance may be shortly stated to consist in causing the wheel 

 which bears the paddles to revolve on one centre, and the radial arms 

 which move the paddles to revolve on another centre. Let ABCDEFGH 

 i K L be the polygonal circumference of the paddle-wheel, formed of 

 straight bars, securely connected together at the extremities of the spokes 

 or radii of the wheel which turns on the shaft which is worked by the 

 engine ; the centre of this wheel being at o. So far this wheel is similar 

 to the common paddle-wheel; but the paddle-boards are not, as in the 

 common wheel, fixed at A B o,.&c., so as to be always directed to the 

 centre o, but are so placed that they are capable of turning on axles which 

 are always horizontal, so that they can take any angle with respect to the 

 water which may be given to them. From the centres, or the line joining 

 the pivots on which these paddle-boards turn, there proceed short arms K, 

 firmly fixed to the paddle-boards at an angle of about 120. On a motion 

 given to this arm K, it will therefore give a corresponding angular motion 

 to the paddle-board, so as to make it turn on its pivots. At the extremi- 

 ties of the several arms marked K is a pin or pivot, to which the 

 extremities of the radial arms L are severally attached, so that the angle 

 between each radial arm L and the short paddle arm K. is capable of being 



153 



