452 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK iv. 



adding its impulse to that of the former and in this way the ship 

 was moved. The names of Shorter (1802), Samuel Brown (1825), the 

 clever French . Captain Delisle (1823), the brothers Bourdon and 

 Savage (1832), should be quoted in the list of those who have con- 

 ceived plans or made attempts towards the application of the screw 

 to propelling ships. 



Two men an English mechanic, Smith, formerly a simple farmer, 

 and the Swedish engineer, Ericson may be considered as having 

 definitely and almost simultaneously solved the problem. 



The Archimedes, a steamship of 90 horse-power, was the first vessel 

 which was driven by the action of one of Smith's screw-propellers in 

 1838. Four years later the Princeton of 220 horse-power, provided 

 with an Ericson's screw was launched in the United States. 



The first attempts of the Swede Ericson were made in England. 

 A ship called the Francis B. Qyden, provided with his propeller, 

 towed a schooner of 140 tons burden, at the rate of seven miles an 

 hour. But Ericson having received no encouragement in England 

 went to the United States, where his invention was received with the 

 enthusiasm it deserved. He had allied himself before his departure 

 with Stockton, a naval officer of the United States, and it was on the 

 Robert Stockton, a screw steamer of seventy horse-power, that they 

 crossed the ocean together, and disembarked on the coasts of the 

 great Eepublic. The Princeton soon followed this first English 

 constructed boat. 



In 1842, France followed the example set by the two great mari- 

 time powers. A ship of 130 horse-power provided with an Ericson 

 screw was constructed at Havre. 



Since that time the transformation of fleets into screw steamships 

 has made great progress in the world. Merchant vessels and packets 

 followed the example, without the system of paddle-wheel propellers, 

 which also has its advantages, being altogether abandoned. This 

 is not the place to give the history of these changes ; we return, 

 therefore, to the description of the different screws adopted, and 

 then take up again that of marine steam-engines which are more 

 particularly our study. 



Smith's first screws were formed of a whole turn round the axis ; 

 later he reduced the screw to a half turn, but doubled it (Fig. 307). 

 Experience soon showed that the extension of the spire in the 



