"If strong boilers to stand 200 lbs. to the inch are made with small tubes, I have no doubt but that the duty would be considerably more, and my engines will not be one-quarter part of the weight, price, or space of others; and when every advantage is taken it will be 1000 per cent. superior in saving of coal to those now at work on board. This engine works well, and returns the steam very regularly every stroke into the boiler. "I am extremely sorry you were not present to see these experiments. Please make your remarks on these statements, with any further information you may judge useful. "I shall now make drawings agreeable to my experiments for actual performance on board ships. In hope of hearing from you soon, "I remain, Sir, "Your very humble servant, "RICHD. TREVITHICK." The large old boilers used as surface condensers, in which the steam was partially condensed by the transmission 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,[173] he wrote in June, 1830:-- [Footnote 173: Drawing of iron steamship, vol. i., p. 336.] "TO THE RIGHT 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 invention entirely removes the great objection of feeding the boiler with salt water." This petition was backed by Mr. Gilbert and Mr. George Rennie. His old friend Mr. Mills took an interest in it, and wrote, "I am going to meet Captain Symonds at Woolwich again to-morrow, and hope to be able to persuade him to use his influence with Sir T. Hardy," "LAUDERDALE HOUSE, HIGHGATE, "MR. GILBERT, "_August 19th, 1830_.