384 HALL'S CONDENSER. 







" Mr. Kennie was engaged for many years in urging the intro- 

 duction of steam-power in the Royal Navy. In 1817, we find 

 him writing to Lord M<4ville, Sir J. Yorke, Sir D. Milne, and 

 others on the subject. In July, 1818, he laments that he 

 cannot convince Sir G. Hope or Mr. Secretary Yorke of their 

 utility, but that he is persuaded their adoption must come at 

 last. On the 30th May, 1820, he writes James Watt, of Bir- 

 mingham, informing him that the Admiralty had at last decided 

 upon having a steamboat, notwithstanding the strong resistance 

 of the Navy Board." l 



So that Mr. Bennie, as professional adviser of the 

 Navy Board, had to persuade for three years, with a 

 knowledge of Trevi thick's prior experiments, before 

 active steps were agreed to ; for twelve years had then 

 passed since Trevithick's nautical labourer and iron 

 steamboat had been tried on the Thames, and five since 

 his experiments with the screw-propeller. 



An article in ' The Times ' gives in strong contrast 

 the relative value of screw and paddle-wheels as pro- 

 pellers. The 6 Syria ' was originally a paddle-wheel 

 steamer, having oscillating cylinders worked with steam 

 of 25 Ibs. on the inch, and Hall's tubular condenser ; 

 after a time the paddle-wheels were removed for a screw- 

 propeller, driven by two steam-cylinders side by side, 

 of different diameters, the high-pressure steam exerting 

 its full force in the small cylinder, and then expanding 

 in the larger cylinder. All the leading features in this 

 improved steamboat of the present day, such as high- 

 pressure expansive steam in one or two cylinders, with 

 tubular condenser and screw-propeller, had been pub- 

 licly proved by Trevithick fifty years before. 



" Screw against Paddle. An interesting and important trial 

 trip has recently been made, which serves to exhibit the advan- 



1 ' Lives of the Engineers,' by Smiles, vol. ii., p. 267, 



