504 INVENTION OF THE STEAM-BLAST. APPENDIX. 



being extended a less intense blast is required. The orifices 

 of the blast-pipes of many engines running at the present day 

 are as large as the steam ports. Consequently they cannot 

 be said to be contracted at all. In fact the greater apparent 

 efficiency of the steam-blast, as at present used, is entirely 

 due to the greater velocity of the piston." 



In a subsequent letter to us, Mr. Stephenson added the 

 following remarks : 



" In conclusion, let us suppose that Hack worth really did first 

 contract the blast-pipe, does that at all affect the claim of 

 George Stephenson to have been the first discoverer of the fact 

 that throwing the eduction steam in the form of a vertical jet 

 into the chimney, greatly increased the power of the locomotive 

 engine ? As well might it be contended that James Watt had 

 no merit for his invention of the steam-engine, because its 

 effectual performance has been so greatly improved since his 

 death. 



" The value of an invention does not consist merely in the 

 results which are immediately produced by it, but in those 

 which quickly follow. But in the case of that modification of 

 the invention in question, it has been found that other circum- 

 stances have attended the progress of the locomotive engine, 

 which have rendered the contraction of the blast-pipe compara- 

 tively unnecessary, and in some cases positively objectionable." 



We trust that the explanations thus given will have made 

 it sufficiently clear to the reader that the claims respectively 

 made on behalf of Trevithick, Hedley, Hackworth, and Gurney, 

 of having invented the steam- blast, are without foundation ; 

 and that George Stephenson, and no other person, was its sole 

 inventor. 



