262 M. Arago's Biographical Memoir of James Watt. 



Power, however, it should be observed, is not the only ele- 

 ment of success in the labours of industry. Regularity of 

 action is of scarcely less importance ; and what degree of re- 

 gularity is to be expected from a moving power which is pro- 

 cured from the fire, under the influence of the poker and 

 shovel, and supplied by coals of very difl'erent qualities, under 

 the influence, too, of workmen often far from intelligent, and 

 almost always inattentive \ We should expect that the pro- 

 pelling steam would be sometimes superabundant ; that hence 

 it would rush into the cylinder with the greater rapidity, so 

 making the piston work more rapidly according as the fire was 

 more powerful ; and from such causes great inequalities of 

 movement appear almost inevitable. But for all irregularities 

 of this sort the genius of Watt provided a remedy. The 

 valves through which the steam proceeds from the boiler to 

 enter into the cylinder, have a variable area. When the 

 speed of the machine is accelerated, these valves partially 

 close, hence the steam enters less freely, and the acceleration 

 is arrested : ^and, on the contrary, when the movement re- 

 laxes, then the apertures of the valves are increased. The 

 mechanism which is necessary for effecting these different 

 changes, connects the valves with an apparatus whose principle 

 Mr Watt exhibited in the regulator of the sluices of cer- 

 tain flour-mills, and which he denominated the governor., but 

 which is now commonly called the regulator hy centrifugal force. 

 Its efiicacy is such, that a few years since there was to be seen 

 at Manchester, in the cotton-mill of Mr Lees, a mechanist of 

 great talent, a clock, which was set in motion by the steam- 

 engine of the establishment, and which kept time, without 

 any marked inferiority, with an ordinary clock of the common 

 construction. 



The regulator of Watt, and a skilful employment of fly- 



rectly pumping out the water : he believed that this liquid thus raised to 

 the necessary height should then be thrown into the troughs, or poured upon 

 the boards of common hydraulic wheels. The anticipations of Mr Smeaton 

 have not in these respects been confirmed. Nevertheless, I saw, in the 

 year 1834, in Mr Boulton's establishment at Soho, an old steam-engine, 

 which is still employed in raising water from a large pond, and then throw- 

 ing it upon the buckets of a large water-wheel, which was used when, in 

 particularly dry seasons, the usual supply was not sufficient. 



