AND SURFACE CONDENSKK. 335 



eluded water, and affords by its partial condensation 

 a supply for the boiler itself." l 



Not one of his numerous patent specifications has 

 been found among his papers, neither do his letters 

 refer to them ; probably he never read them after the 

 first necessary examinations. 



" MR. GILBERT, " HAYLE FOUNDRY, November 5$, 1829. 



" Sir, The engine has been worked. The result is ten 

 strokes per minute, 6-feet stroke, with half a bushel of coal per 

 hour, lifting six thousand pounds weight. This was done with 

 water in the cistern round the condenser, which water came up 

 to 180 degrees of heat, and remained so. The water sides of 

 the condenser covered with this hot water was 50 surface feet. 

 I tried it to work with the cold air sides, but I found that the 

 cold air sides of 120 feet would only work it four strokes per 

 minute. I should have worked the steam much higher than 

 50 Ibs. to the inch, but being an old boiler I thought it a risk. 

 I am now placing an old boiler of 350 feet of cold sides more to 

 the condenser, to give a fair trial to condensing with cold sides 

 alone. The steam below the piston was about 6 or 7 Ibs. to 

 the inch above the atmosphere. The force-pump to the boiler 

 was about one-fifth part of the content of the cylinder, and the 

 valve close to the boiler lifted when the force-piston was down 

 about two-thirds of its stroke, at which time the returned steam 

 entered the boiler again. I have no doubt of doing near ten 

 times the duty that is now done on board ships, without using 

 salt water in the boiler, as at present. Our boiler has been 

 working three days and the water has not sunk 1 inch per day. 

 I am quite satisfied the trial will be a great success. 



" Mr. Praed and Sir John St. Aubyn are anxious to get a high 

 bank carried out from Chapel Angel to 15 feet below low-water 

 mark on the bar, to make Hayle a floating harbour. 



"I have proposed to make a sand-lifting engine. When I 

 built that engine for deepening Woolwich Harbour, we lifted 

 .' >00 tons per hour through 36 feet of water, and 20 feet above 



1 Sec patdit specification of 1802, vol. i., p. 128. 



