ROBERT STEPHENSON'JS NARRATIVE. 503 



the exception that the two eduction-pipes were brought into one 

 blast-pipe in the centre of the chimney. The tw r o engines might 

 therefore be considered as precisely alike in principle. 



" With respect to the objection which has been made in 

 * The Engineer,' to two separate orifices, I must affirm that no 

 remark could possibly be more unfounded. The writer states 

 that w r hen two separate orifices are employed, the blast produced 

 by one is neutralized by the other. The ' Rocket ' worked 

 perfectly well with the double blast-pipe, and, to the best of my 

 recollection, the prize was won without any alteration having 

 been made in that part of the engine. 



" The experiments already mentioned proved that the double 

 blast -pipe in the * Rocket ' was capable of producing a con- 

 siderable rarefaction in the chimney, and the alteration from 

 two blast-pipes to one was made by myself rather with a view of 

 lessening the space occupied by them in the chimney. 



" The writer in ' The Engineer ' completely ignores the fact of 

 the single steam-blast having been in existence eleven years prior 

 to the opening out of the Stockton and Darlington Railway, and 

 seems to argue that tli3 ' Sanspareil ' was the first engine to 

 which the steam-blast was ever applied with effect ; whereas it 

 had actually been in regular use since the year 1814, and the 

 only alteration which it underwent, was the contraction of the 

 orifice made on the Stockton and Darlington Railway some 

 time between the years 1825 and 1827. 



" Whatever merit or value may attach to this alteration I 

 believe to be due to Timothy Hackworth, but nothing beyond 

 it, I am quite certain ; and even this was decidedly much 

 overrated by him : in fact, he carried the contraction to such an 

 extent that nearly half of the fuel was thrown out of the 

 chimney unconsunied, as many can testify who witnessed the 

 experiments at Rain Hill. 



" But surely such an alteration is not to deprive George 

 Stephenson of the merit of the invention of the steam-blast. 

 ^Moreover the contraction in many of our best locomotive engines 

 is totally unnecessary and rather disadvantageous than otherwise ; 

 for, since the speed of the engines has been increased, the velocity 

 of the eduction steam is quite sufficient to produce the needful 

 rarefaction in the chimney without any contraction whatever. 

 In the early engines, when the speed of the piston was slow, the 

 contraction was undoubtedly advantageous, but now that the 

 boilers have been increased in size the heating surfaces thereby 



