Propeller for Steam Ships. 7 



velocity is obtained by shortening the crank and the stroke 

 of the piston and thereby increasing the number of strokes 

 and revolutions of the engine. But this shortening of the 

 crank greatly increases the friction and consequent loss of 

 power. If the velocity of the piston could be increased to 

 any required rate it would simply be necessary to connect 

 the piston-rod to the shaft of this propeller, and the whole 

 force of the steam would thus be available for direct propul- 

 sion, without parallel motion, levers, or other gearing, and an 

 immense saving would be effected in the weight of the 

 engines. In the Terrible steam ^frigate of 1 847 tons, and 

 800 horse-power, the contract weight of the engines was 212 

 tons, and the weight of the paddle wheels 44 tons. 



There seems to me no sufficient reason why the present 

 speed of the piston should not be greatly increased. If a great 

 object is to be gained by an increased speed, a corresponding 

 effort must be made to surmount the difficulties that may 

 interpose, and there is no doubt, I think, that a greatly in- 

 creased speed could be obtained by lengthening the cylinder, 

 and using high pressure steam. 



Until this is accomplished it will be necessary to multiply 

 the velocity of the piston, by means of levers, and to prevent 

 any loss of power from the reciprocating motion of the levers, 

 by means of the equalising air cylinder. The science of 

 hydraulics in its application to propulsion is confessedly 

 difficult to be understood, and no theory will be accepted as 

 the present time that is not amply supported by experimental 

 proof. Experiments properly conducted for testing the 

 capablities of this propeller, and its comparative value, would 

 involve a large expenditure of time and money, and I have 

 therefore no experimental proof at present to offer in support 

 of its alleged advantages. But the principle on which it is 

 constructed is so obvious, and its construction is so simple, 

 that careful theoretical deductions with regard to its practical 

 application are not likely to deviate much from the truth. 



In the position where the propeller is intended to work, 

 the water will have a slight retrograde motion, partly in- 

 duced by the action of the propeller, and partly by the collapse 

 of the water in the wake of the ship when in motion. 



At the commencement of each stroke, the floats will 

 rapidly expand until they come to rest on the shoulder 

 attached to the shaft, in which position the floats will be at 

 right angles to the course of the ship, and will present the 

 whole of their surface in the most favourable position for 



