THE CONQUEST OF TIME AND SPACE 



and in practice this engine showed several points of supe- 

 riority over its predecessors. It would draw eight loaded 

 wagons of thirty tons' weight at the rate of four miles 

 an hour on an ascending grade of one in four hundred 

 and fifty feet. But it had two very radical defects — it 

 would not keep up steam and the noise of the steam- 

 pipe exhausting into the open air frightened the horses 

 of the neighborhood to such a degree that the author- 

 ities ordered the inventor either to stop running his 

 engine, or suppress its noise. As an experiment, there- 

 fore, Stephenson arranged the exhaust pipes so that 

 they opened into the smokestack, where the sound 

 would be muffled. But when the engine was now tried 

 he found to his surprise that this single expedient had 

 solved both difficulties, the exhausting steam causing 

 such an improvement in the draught of his furnace 

 that double the quantity of steam was generated. This 

 discovery helped to simplify later experiments, for the 

 difficulty of keeping up steam had been one of the 

 great obstacles encountered by the inventors. 



Stephenson's second locomotive was an improve- 

 ment over his first in many ways, but it was still far from 

 being the practical machine that was to supplant horse- 

 power. It could haul heavier loads than teams of 

 horses, and was more convenient for certain purposes; 

 but it was no more economical. 



As yet the only use to which locomotives had been 

 put was that of hauling cars in coal-mines. Indeed, the 

 only railroads then constructed were those used in 

 mines, the idea of utilizing such roads for passenger 

 and freight traffic not having occurred to anyone until 



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