100 



THE STEAM-BLAST. 



CHAP. VI. 



The steam, after performing its duty in the cylinders, 

 was at first allowed to escape into the open atmosphere 

 with a hissing blast, to the terror of horses and cattle. 

 It was complained of as a nuisance ; and a neighbouring 

 squire threatened to commence an action against the 

 colliery lessees unless it was put a stop to. But Mr. 

 Stephenson's attention had already been drawn to the 

 circumstance of the much greater velocity with which 

 the steam issued from the exit pipe compared with that 

 at which the smoke escaped from the chimney of the 

 engine. He then thought that, by conveying the 

 eduction steam into the chimney by means of a small 

 pipe after it had performed its office in the cylinders, 

 and allowing it to escape in a vertical direction, its 

 velocity would be imparted to the smoke from the fire, 

 or to the ascending current of air in the chimney, 1 

 thereby increasing the draft, and consequently the 

 intensity of combustion in the furnace. 

 I The experiment was no sooner made than the power 

 of the engine was at once more than doubled ; com- 

 bustion was stimulated by the blast ; consequently the 

 capability of the boiler to generate steam was greatly 

 increased, and the effective power of the engine aug- 

 mented in precisely the same proportion, without in any 

 way adding to its weight. This simple but beautiful 

 expedient was really fraught with the most important 

 consequences to railway communication ; and it is not 

 too much to say that the success of the locomotive 

 depended upon its adoption. Without the steam-blast, 

 by which the intensity of combustion, and the conse- 

 quent evolution of steam, were maintained at their 

 highest point, high rates of speed could not have been 

 maintained, the advantages of the multitubular boiler 

 (afterwards invented) could never have been fairlv 



1 The subject of the Steam Blast, 

 land the various claims which have 

 {been made as to its invention, will be 



found discussed at some length in t he- 

 Appendix to this work. 



