10 On a New Form of 



propeller might be connected directly to the piston-rod with- 

 out levers. 



I shall not here consider what loss of power, if any, results 

 from the use of the crank. It is obvious that the friction 

 must be very great when the crank is short, as it necessarily 

 must be to obtain speed, both with the paddle wheels and 

 screw. 



By the proposed arrangement the whole effective force of 

 the steam is more simply, and more immediately, and more 

 directly expended in direct propulsion. 



If, however, the proposed levers be found objectionable 

 for marine purposes, the reciprocating motion of the propel- 

 lers might be obtained through the medium of a wheel and 

 crank with continuous motion, — the connecting rods of the 

 two shafts being attached to opposite ends of the diameter 

 of the wheel. 



But it appears to me that no object is to be gained by 

 employing the continuous rotatory motion of the crank, 

 while the disadvantages arising from the great length and 

 oblique action of the connecting rods would outweigh any 

 advantages which continuous motion might possess in other 

 respects. If therefore, levers, are objectionable, the recipro- 

 cating rectilinear motion of the propellers may be effectively 

 obtained by means of toothed wheels. The shaft of each 

 propeller being provided with teeth, both on its upper and 

 under surface, a large toothed wheel would be placed cen- 

 trally between the shafts, and a reciprocating motion com- 

 municated to the wheel would give an alternate reciprocating 

 motion to the propellers. 



To secure the shafts of the propellers in their position, 

 with the least amount of friction, two toothed wheels of 

 smaller diameter would be required, — the one to work into 

 the teeth on the upper surface of the upper shaft, the other 

 into the teeth on the under surface of the lower shaft. 



Any required length of stroke would be obtained by 

 means of a multiplying wheel, to which a reciprocating 

 motion is given by a connecting rod and crank. 



The diagram in Plate III. will illustrate the relative 

 position of the wheels, and the shafts of the propellers. 



Toothed gearing has been frequently employed to multiply 

 the velocity of the screw, and although objectionable from 

 its liability to derangement, it has important advantages 

 in combining economy of space with great length of stroke. 



