84 Book of Locomotives 



many of his compeers might have hesitated ; 

 he went right outside for his design and 

 its construction. The success of the water- 

 tube boiler has been demonstrated so clearly 

 in naval ships that it is now becoming the 

 standard on certain types of commercial 

 craft. What then more reasonable than that 

 this clever engineer should consider the 

 question of applying it to the locomotive? 



But he did not go farther with the idea 

 until he had ascertained beyond all manner 

 of doubt that there was a reasonable chance 

 of its success on wheels. We must never 

 overlook that as regards stationary, marine, 

 and locomotive boilers each presents an 

 entirely different problem, particularly 

 when, as in the first two cases, the demand 

 for steam is more or less regular, whereas 

 in the case of the locomotive it varies with 

 every mile that the engine runs. 



After experiment Mr. Gresley determined 

 that his water-tube boiler should be pressed 

 to 450 Ib. which, observe, is exactly double 

 that of the highest regularly used on any 

 number of British engines. This huge 



