6 On a New Form of 



Length of stroke being essential for speed the levers must 

 be proportionably long, but it is also necessary to multiply 

 the speed of the piston by attaching the connecting-rod to 

 the leVers proportionably near to the fulcrum. 



a b and c d represent the levers, a and c being the 

 fulcra on which they move. The lever a b is extended 

 to i for the purpose of connecting the action of the two 

 cylinders, and concentrating the power of both cylinders 

 upon each propeller alternately, by means of the connecting- 

 rod i h. g and h represent the cylinders, and d e and bf 

 the propellers. 



For the purpose of reversing the action of the propellers 

 a moveable inclined plane will be fixed at each end of the 

 stroke of the shaft within the ship, and when it is required 

 to reverse the action the inclined plane will be placed in 

 position to raise the projecting lever attached to the inner 

 tube of the shaft. The rotation of the shoulder will thus be 

 rapidly effected at the proper time without stopping the 

 piston. 



The first requirement in steam propulsion is speed, and at 

 first sight the propeller which I have just described may seem 

 only suited for low rates of velocity. 



In low-pressure marine engines the speed of the piston 

 averages about 250 feet per minute. Any required speed in 

 the propeller, however, could be obtained by means of levers, 

 as shown above. 



But to obtain very high rates of speed with this propeller, 

 or indeed with any other method of propulsion, it will be 

 necessary to adopt high-pressure steam in marine engines. 



Hitherto steam vessels have been built, not exclusively for 

 speed, but rather with the view of combining speed with 

 carrying power. 



For "the purposes of modern mail communication speed 

 ought to be almost exclusively aimed at, and when ships are 

 built on this principle it will be necessary to abandon the 

 ponderous low-pressure or condensing engines, and to adopt 

 light high-pressure engines, similar in principle to those found 

 so effective in locomotives on railways. 



The greater speed of the piston in high-pressure engines, 

 which reaches 500 feet per minute, would add greatly to the 

 efficacy and speed of this propeller. 



In applying steam power to give motion to the paddle 

 wheels and screw, it is necessary to convert the reciprocating 

 motion of the piston into a continuous rotatory motion, which 

 is effected by means of the crank, and in direct-acting engines 



