Victory of the "Rocket" Locomotive 



a mode of overcoming the difficulty, which, his 

 son had already anticipated and proceeded to 

 adopt. It was, to bore clean holes in the boiler 

 ends, fit in the smooth copper tubes as tightly 

 as possible, solder up, and then raise the steam. 

 This plan succeeded perfectly, the expansion of 

 the copper tubes completely filling up all inter- 

 stices, and producing a perfectly water-tight 

 boiler, capable of withstanding extreme external 

 pressure. 



The mode of employing the steam-blast for 

 the purpose of increasing the draught in the 

 chimney was also the subject of numerous ex- 

 periments. When the engine was first tried, it 

 was thought that the blast in the chimney was 

 not sufficiently strong for the purpose of keeping 

 up the intensity of fire in the furnace, so as to 

 produce high-pressure steam with the required 

 velocity. The expedient was therefore adopted 

 of hammering the copper tubes at the point at 

 which they entered the chimney, whereby the 

 blast was considerably sharpened; and on a far- 

 ther trial it was found that the draught was in- 

 creased to such an extent as to enable abundance 

 of steam to be raised. The rationale of the 

 blast may be simply explained by referring to the 

 effect of contracting the pipe of a water-hose, 

 by which the force of the jet of water is pro- 

 portionately increased. Widen the nozzle of 

 the pipe, and the jet is in like manner diminished. 

 So it is with the steam-blast in the chimney of 

 the locomotive. 



175 



