Masterpieces of Science 



pool and Manchester Railway embankments, was 

 constructed with a double tube, each of which 

 contained a fire, and passed longitudinally 

 through the boiler. But this arrangement 

 necessarily led to a considerable increase in the 

 weight of those engines, which amounted to 

 about twelve tons each; and as six tons was 

 the limit allowed for engines admitted to the 

 Liverpool competition, it was clear that the 

 time was come when the Killingworth engine 

 must undergo a farther important modification. 



For many years previous to this period, in- 

 genious mechanics had been engaged in attempt- 

 ing to solve the problem of the best and most 

 economical boiler for the production of high- 

 pressure steam. 



The use of tubes in boilers for increasing the 

 heating surface had long been known. As early 

 as 1780, Matthew Boulton employed copper 

 tubes longitudinally in the boiler of the Wheal 

 Busy engine in Cornwall the fire passing 

 through the tubes and it was found that the 

 production of steam was thereby considerably 

 increased. The use of tubular boilers afterwards 

 became common in Cornwall. In 1803, Woolf, 

 the Cornish engineer, patented a boiler with 

 tubes, with the same object of increasing the 

 heating surface. The water was inside the tubes, 

 and the fire of the boiler outside. Similar ex- 

 pedients were proposed by other inventors. In 

 1815 Trevithick invented his light high-pressure 

 boiler for portable purposes, in which, to " expose 

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