CATALOGUE OF THE WATEKCRAFT COLLECTION. 57 



are shown attached to the hub by a round bar or shank fitting into 

 a corresponding hole in the hub and with its axis perpendicuhxr to 

 that of the propeller shaft so that the pitch can be adjusted by 

 slightly turning the bar or shank in the hub. 

 Purchased. Cat. No. 180,597 U.S.X.M. 



INTRODUCTION OF THE SCREW PROPELLER. 



Water wheels for mills, driven by the action of a current against 

 their vanes or blades, placed obliquely to the direction of the cur- 

 rent, have been used in China for centuries and in Spain from the 

 time of its conquest by the Moors. Prior to the revolution they 

 were in use in this country for mills, and were called Chinese 

 sculls or tub wheels. In principle this wheel is identical w4th the 

 windmill, and when attached to a vessel and driven by power ap- 

 plied to a shaft it is a screw propeller. 



Colonel Stevens, in his letter to Doctor Hare, quoted earlier, con- 

 sidered himself its inventor for the propulsion of vessels, but he was 

 mistaken. It was proposed by the mathematician, Daniel Bernouli, 

 in 1752. and it is described by David Bushnell in a letter to Thomas 

 Jefferson, dated 1787, giving an account of his submarine boat to 

 which a screw propeller, worked by hand, was applied, and of his 

 attempt, with this boat, to blow up a 50-gun British ship in the 

 harbor of New York. 



The same idea of the propulsion of vessels by means of spiral 

 wheels was afterwards suggested by Franklin, Watt, Paucton, anil 

 others. 



Previous to the year 1802 the screw propeller was twice distinctly 

 patented in England, and the invention was described in each patent 

 by a specification and drawing. The patent to William Lyttleton 

 was granted in 1794. 



This screw propeller was a long spiral wheel, revolved by an 

 endless rope on a pulley worked by manual labor. It was tried on 

 a vessel at the Greenwich Dock, London, and a speed of 2 miles an 

 hour was said to have been attained. The second patent was granted 

 to Edward Shorter in 1800. Shorter had two plans, one a form of 

 duck-foot paddles with an alternate movement, often proposed and 

 tried before and since; the other a two-bladed screw propeller at- 

 tached to an inclined shaft carried by a universal joint to the deck 

 of the vessel. By one of Shorter's plans, but by which one is un- 

 certain, the transport Dencaster was said to have been propelled at 

 a speed of 1^ miles an hour by eight men working at a capstan. 



The first application of steam to a screw propeller was made by 

 Colonel Stevens on the Hudson River in the year 1802. His experi- 

 ments in screw propulsion began in 1801 and were continued until 

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