372 MARINE STEAM-ENGINES. 



by a catch until the return movement, so that when it 

 propelled, its whole surface pressed against the water, 

 and when moving in a contrary sense, only its edge 

 offered resistance to the water. 



The writer has no record of the practical application 

 of the duck's foot as a steamboat propeller; but the 

 portable puffer-engine now pulls on board the fisher- 

 man's heavy nets, and the magnificent steamer 'Adriatic' 

 hoists her sails on iron yards and masts by six of those 

 steam helps. 1 



Twenty years before he had solicited the Navy Board 

 to try his iron ships propelled by high-pressure steam- 

 engines, and had shown their applicability as steam- 

 dredgers ; and again, shortly after his return from 

 America, he pressed on their attention the same subject 

 under new forms, followed by communications with 

 their engineer, Mr. Rennie, and a proposal to place an 

 engine in a boat at his own cost. 



The writer has attempted in this and the preceding 

 chapter to classify Trevithick's schemes, crowded to- 

 gether in those last years of his life, but the subjects 

 so run into one another that the acts of twenty years 

 before must be borne in mind to enable the more modern 

 plans to be understood. 



The letter introducing the surface condenser, in 1828, 

 at the commencement of the former chapter, was in a 

 month followed by that recommending a particular kind 

 of paddle to be used as auxiliary steam-power, and after 

 six months of experiments, by the patent of 1831, and 

 the following correspondence : 



" ME. GILBERT, " LAUDERDALE HOUSE, HIGHGATE, June 10th, 1830. 



"Sir, Yesterday I saw Mr. George Kennie, and he 

 requested me to write to the Admiralty, a copy of which I send 



1 See 'Illustrated News,' 27th April, 1872. 



