376 MARINE BOILER AND ENGINE. 



the eminent marine-engine builders whom he served, 

 was told that the lightness of the engine would cause 

 less profit to the makers. Their bills were based on the 

 pouilds weight delivered, and new designs necessitated 

 new patterns and new troubles. It was unreasonable 

 to expect those makers of marine steam-engines to 

 report that Trevi thick knew better than they did. 

 They knew of his screw-propeller experiments fifteen 

 years before, but they in no way benefited him, and the 

 Admiralty Captain was either a tool in their hands, or 

 powerless without them. 



The primary object, when the loan of the ship was 

 asked, was the using for marine purposes a high- 

 pressure steam tubular boiler, combined with tubular 

 condenser, supplying or returning its water as feed, 

 thereby avoiding the use of salt water in the boiler ; 

 arid this steam-engine, as shown in his patent of 1831, 

 was to be applied either to his screw, or his duck's foot, 

 or other propeller ; but during the year or two of 

 suspense, other schemes for propelling ships had occu- 

 pied his thoughts, resulting in the patent of 1832. 



Steam-Engines, 1832. 



" Now KNOW YE, that in compliance with the said proviso, I, 

 the said Bichard Trevithick, do hereby declare the nature of 

 my said invention, as regards the improvement or improvements 

 on the steam-engine, to consist in interposing between the boiler 

 and the working cylinder, in a situation to be strongly heated, 

 a long pipe formed of a compact series of curved or bent pipes, 

 which I denominate the dry pipes, or steam-expanding appa- 

 ratus, through which dry pipes I cause the steam, after it lias 

 been generated in the boiler in contact and consequently satu- 

 rated with water, to pass with very great velocity, in order that 

 it may imbibe a copious supply of additional heat without any 

 addition of water, and by this additional heat to be expanded 



