THROTTLE VALVE AND GOVERNOR. 403 



Power is not the only element of success in industrial 

 works. Regularity of action is not less important ; but 

 what regularity could be expected from a motive power 

 engendered by fire fed by shovels full, and the coal itself 

 of various qualities ; and this under the direction of a 

 workman, sometimes not very intelligent, almost always 

 inattentive ? The motive steam will be more abundant, 

 it will flow more rapidly into the cylinder, it will make 

 the piston work faster in proportion as the fire is 

 more intense. Great inequalities of movement then ap- 

 pear to be inevitable. Watt's genius had to provide 

 against this serious defect. The throttle-valves by which 

 the steam issues from the boiler to enter the cylinder are 

 not constantly open. When the working of the engine 

 accelerates, these valves partly close ; a certain vol- 

 ume of steam must therefore occupy a longer time in 

 passing through them, and the acceleration ceases. The 

 aperture of the valves, on the contrary, dilates when the 

 motion slackens. The pieces requisite for the perform- 

 ance of these various changes connect the valves with 

 the axes which the engine sets to work, by the introduc- 

 tion Translator): "I was myself surprised at the regularity of its 

 action. When I saw it work for the first time, I felt truly all the 

 pleasure of novelty, as if I was examining the invention of another 

 man.'" 



Smeaton, who was a great admirer of Watt, did not believe, how- 

 ever, that it could in practice become a general and economical 

 means of impressing directly rotatory motion to axes. He maintained 

 that steam-engines would always be more serviceable in pumping 

 water direct. This fluid having reached a suitable height, was then to 

 be thrown into the trough, or on to the pallets of common hydraulic 

 wheels. In this respect the prophecies of Smeaton were not realized. 

 Yet, in 1834, on visiting the establishment of Mr. Boultou at Soho, I 

 saw an old steam-engine still employed to raise water from a large 

 pool, and pour it into the troughs of a great hydraulic wheel, when 

 the season being ver} r dry the water-power was insufficient. 



