CHAP. VIII. STEPHENSON'S STEAM SPRINGS. 133 



from cast to malleable iron, in whole or in part, by 

 which they were made lighter as well as more durable 

 and safe. But the most ingenious and original con- 

 trivance embodied in this patent was the substitute for 

 springs which Mr. Stephenson invented. He contrived 

 that the steam generated in the boiler should perform 

 this important office. The method by which this was 

 effected displayed such genuine mechanical genius, that 

 we would particularly call the reader's attention to the 

 device, which was the more remarkable, as it was con- 

 trived long before the possibility of steam locomotion 

 had become an object of parliamentary inquiry or even 

 of public interest. 



It has already been observed that up to, and indeed 

 for some time after, the period of which we speak, there 

 was no such class of skilled mechanics, nor were there 

 any such machinery and tools in use, as are now at the 

 disposal of all inventors and manufacturers. Although 

 skilled workmen were in course of gradual training in a 

 few of the larger manufacturing towns, they did not, at 

 the date of Stephenson' s patent, exist in any consider- 

 able numbers, nor was there then any class of mechanics 

 capable of constructing springs of sufficient strength 

 and elasticity to support locomotive engines of ten tons 

 weight. 



In order to avoid the dangers arising from th< 

 inequalities of the road, Mr. Stephenson so arranged 

 the boiler of his new patent locomotive that it was 

 supported upon the frame of the engine by four cylin- 

 ders, which opened into the interior of the boiler. 

 These cylinders were occupied by pistons with rods, 

 which passed downwards and pressed upon the upper 

 side of the axles. The cylinders opening into the 

 interior of the boiler, allowed the pressure of steam to 

 be applied to the upper side of the piston ; and the 

 pressure being nearly equivalent to one-fourth of the 

 weight of the engine, each axle, whatever might be its 



