TUBULAti BOILER, VARIABLE BLAST. 387 



national importance seventy years after their discovery, 

 for as far back as that he used highly-expansive steam, 1 

 and on the question of a separate cylinder for expan- 

 sion as used in the modern steamboat combined engines, 

 he wrote, " I think one cylinder partly filled with steam 

 would do equally as well as two cylinders ; that one at 

 Worcester shuts off the steam at the first third of the 

 stroke, and works very uniformly with a considerable 

 saving of coal. 2 Those modern marine engines use about 

 the same steam pressure and expand about in the same 

 proportion. With the direct action from the piston-rod 

 to the crank-shaft, the multitubular boiler and screw- 

 propeller, and the surface condenser perfected in 1831 

 and 1832, at which time his construction of a marine 

 steam-engine would have been just what it now is forty 

 years later. Those latter patents also embrace the 

 principle of superheating steam, practically shown 

 many years before, 3 and still used by marine engineers 

 of modern times. 



In tracing the wisdom of his designs just before the 

 close of an eventful life, reference may be made to the 

 trial of a common road locomotive in 1871 : "Experi- 

 mental trip of the Indian Government steam, train 

 engine, 'Ranee,' from Ipswich to Edinburgh. The 

 results of the trial with the ' Chenah,' though satis- 

 factory so far as the engines proper were concerned, 

 were vitiated by the failure of the boiler ; on the com- 

 pletion of the second engine, the 'Ranee,' the field 

 boiler and variable blast- pipe were used ; the boiler is 

 about 4 feet diameter at the bottom and 8 feet high." 4 



The form and dimensions of the exterior of the Ranee 



1 See Trevithick's letter, 22nd 3 See Trevithick's letter, 16th May, 

 August, 1802, vol. i., p. 153. 1815, vol. i., p. 370. 



2 See Trevithick's letter, 5th July, - 4 'The Engineer,' 27th Octln-r, 

 1804, vol. ii., p. 132. i 1871. 



