MA1UNE STEAM-ENGINES. 369 



miles an hour over and above the other work of the ship, and 

 would neither be so heavy or take so much room as their 

 present cooking house and furnace. I think that two iron 

 paddles, one on each side of the rudder, under the stern, would 

 do this very well ; they would be in dead water, and out of the 

 swell of the sea, and by being deep in the water would have a 

 good resistance. Two paddles, each about 4 feet deep and 

 3 feet wide, would do this, without their rising out of the water ; 

 therefore their stroke would be nearly horizontal. The return 

 stroke would be in the water. Thus, let the paddle stand per- 

 pendicular in the water, two-fifths of its width on one side, and 

 three-fifths on the other side, the centre, which would turn 

 its edge to the water on its back stroke, and its flat to the water 



I I 



BOAT AND PROPELLER. 



on the forward stroke ; it would be light, and out of the way of 

 anything. I have a patent now going through the office for all 

 this, which will also cover the new principle of returning the 

 heat back again, as already described to you. The engine for 

 drawing in Holland will be ready about the end of February, 

 and by that time I shall have a complete portable engine ready 

 for London for discharging, when I shall be in town. 



" I remain, Sir, 



" Your very humble servant, 



"KD. TREVITHICK. 



" P.S. Wheal Towan engine is working with three boilers, 

 all of the same size, and the strong steam from the boilers to 

 the cylinder-case ; the boilers are so low as to admit the con- 

 densed water to run back from the case again into the boiler. 

 They find that this water is sufficient to feed one of these boilers 

 without any other feed-water ; therefore one-third of the steam 

 generated must be condensed by the cold sides of the cylinder- 

 case, and this agrees with the experiments I sent to you from 

 Binner Downs. Wheal Towan engine has an 80-inch cylinder, 



