338 TUBULAR BOILER, SUPERHEATING STEAM, 



The large old boilers used as surface condensers, in 

 which the steam was partially condensed by the trans- 

 mission of heat to the external atmosphere, together 

 with its further condensation in a smaller condenser with 

 cold water around it, so reduced its expansiveness, that 

 a large feed-pump drew the hot water and steam from 

 the small condenser, and forced it back into the boiler 

 without any reduction of quantity ; those temporary 

 contrivances, almost immediately resolved themselves 

 into a condenser made of copper tubes surrounded by 

 cold water. 



Having proved by six months' experiment on a 

 working scale the practicability of the plan which in 

 reality he had invented twenty years before in the iron 

 steamship, 1 he wrote in June, 1830 : 



" To THE EIGHT HONOURABLE THE LORDS COMMISSIONERS 



OF THE ADMIRALTY, &c., &c., &c. 

 " MY LORDS, 



" About one year since I had the honour of attending 

 your honourable Board with proposed plans for the improvement 

 of steam navigation, and as you expressed a wish to see it 

 accomplished, I immediately made an engine of considerable 

 power for the express purpose of proving by practice what I 

 then advanced in theory. I humbly request your lordships will 

 grant me the loan of a vessel of about 200 or 300 tons burthen, 

 in which I will fix at my own expense and risk an engine of 

 suitable power to propel the same at the speed required: no 

 alterations whatever in the vessel will be necessary. When 

 under sail the propelling apparatus can be removed, and when 

 propelled by steam alone, the apparatus outside the ship will 

 scarcely receive any shock from a heavy sea. This new in- 

 vention entirely removes the great objection of feeding the 

 boiler with salt water." 



This petition was backed by Mr. Gilbert and Mr. 



1 Drawing of iron steamship, vol. i., p. 336. 



