THROTTLE VALVE AND GOVERNOR. 408 
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 1884, on visiting the establishment of Mr. Boulton 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 very dry the water-power was insufficient. 
