Polytechnic Association Proceedings. 885 



half their circuit, and pull during the remainder of their circuit, 

 with the exception of two indefinitely brief periods when they are 

 changing from a pushing to a pulling force, when they are neutral. 

 As they near these points, and their lateral motion becomes slower, 

 their pitch becomes correspondingly coarser, so that they ai'e press- 

 ing on the water with equal speed during their entire circuit. The 

 blades while in the after position of the circuit, are seen to have a 

 pitch somewhat coarser than in their forward portion. This is as 

 it should be, as they are acting on water that has received some 

 motion. This corresponds to what is known as the " expanding 

 pitch " in a screw. 



THE ENGINE 



May be described as being of the simplest form of a horizontal 

 steam engine, consisting of merely a frame, cylinder and valve, 

 there being no reversing gear, as the engine is not required to run 

 in but one direction. It is attached directly to the upper end of 

 shaft without any intervening gearing. 



STEERING AND MANCEITV^RING. 



The eccentric is not absolutely stationary, but by suitable con- 

 nections between it and the adjusting lever, it may be turned in any 

 direction by the steersman, and this has the effect of casting the 

 propelling force of the wheel in the same direction. 



For example, if the adjusting lever is turned ahead, the pro- 

 pelling force of the wheel will be cast in the same direction, and 

 the boat will move ahead. K turned aft, the boat will move aft. And 

 so of any other point of the compass. The steersman has only to 

 turn the adjusting lever in the direction he wants the propelling 

 power cast. By slightly inclining the adjusting lever, the boat 

 may be turned gradually to the right or left; by further turning 

 it, the boat may be turned in the shortest and most abrupt curve, 

 even to turning on its own center, and in its own length of water, 

 a movement which is invaluable for naval vessels, or for any others 

 which have not much sea room. By reversing the adjusting lever, 

 which can be done in less than one second of time, the wheel is 

 exerting its full propelling force backwards. This can be done 

 from ten to thirty times, while the ordinary propeller is being 

 reversed once. This feature, in connectien with its ability to turn 

 m very short curves, might be the saving of many vessels in cases 

 of collisions and running; aground. 



