CHAP. VI. STEPHENSON INVENTS THE STEAM-BLAST. 99 



Although a considerable advance upon previous loco- 

 motives, " IJluioher " (as the engine was popularly 

 called) was nevertheless a somew T hat cumbrous and 

 clumsy machine. The parts were huddled together. 

 The boiler constituted the principal feature ; and being 

 the foundation of the other parts, it was made to do 

 duty not only as a generator of steam, but also as a basis 

 for the fixings of the machinery and for the bearings of 

 the wheels and axles. The want of springs was seriously 

 felt ; and the progress of the engine was a succession of 

 jolts, causing considerable derangement to the machinery. 

 The mode of communicating the motive power to the 

 wheels by means of the spur gear also caused frequent 

 jerks, each cylinder alternately propelling or becoming 

 propelled by the other, as the pressure of the one upon 

 the wheels became greater or less than the pressure of 

 the other ; and, when the teeth of the cogwheels became 

 at all worn, a rattling noise was produced during the 

 travelling of the engine. 



As- the principal test of the success of the locomotive 

 was its economy as compared with horse power, careful 

 calculations were made with the view of ascertaining this 

 important point. The result was, that it was found the 

 working of the engine was at first barely economical ; 

 and at the end of the year the steam power and the 

 horse power were ascertained to be as nearly as possible 

 upon a par in point of cost. The fate of the locomotive 

 in a great measure depended on this very engine. It& 

 speed was not beyond that of a horse's walk, and the 

 heating surface presented to the fire being comparatively 

 small, sufficient steam could not be raised to enable it to 

 accomplish more on an average than about four miles 

 an hour. The result was anything but decisive ; and 

 the locomotive might have been condemned as useless, 

 had not Mr. Stephenson at this juncture applied the 

 steam-blast, and by its means carried his experiment to ' 

 a triumphant issue. 



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