Mr. J. Preuas oti a new Steam-Engine Govei-noi: '291 



in the particular case of « Lja-te as undecided, and as per- 

 fectly open to future investigation; but the observations of 

 the present year have produced on my mind a conviction 

 approaching to moral certainty. The history of annual 

 parallax appears to me to be this : in proportion as instru- 

 ments have been imperfect in their construction, they have 

 misled observers into the belief of the existence of sensible 

 parallax. This has happened in Italy to astronomers of the 

 very first reputation. The Dublin instrument is superior to 

 any of a similar construction on the continent ; and accord- 

 ingly', it shows a much less parallax than the Italian astrono- 

 mers imagined they had detected. Conceiting that I have 

 established, beyond a doubt, that the Greenwich instrument 

 approaches still nearer to perfection, I can come to no other 

 conclusion than that this is the reason why it discovers no 

 parallax at all. 



LXII. On a new Steam-Engine Governor. By Mr. J. Preuss, 

 of Hanover, Engineer, late Insj^ector-General of French 

 Imperial Forests, Felloio of several learned Societies*. 



TT has been observed by Mr. DooHttle of America, that the 

 well-known centrifugal steam-engine governor, invented by 

 the celebrated James Watt, is a less perfect regulator of velocity 

 than might be wished lor, particularly for purposes which re- 

 quire a great regularity and nicety ui the motion of the steam- 

 engine ; as for instance, in cotton mills, &c. Indeed the cen- 

 trifugal forces of two equal masses which perform their revo- 

 lutions round a central point in equal times, being to each 

 other as the radii of the described circles, it follows, that if 

 the two balls revolved with an adequate speed, so that their 

 centrifugal force, which tends to make them fly asunder, was 

 exactly counterbalanced by their weight, which tends to make 

 them collapse, they would continue in their places, but without 

 exerting any pressure upon them. 



Let us suppose now that their speed happened to increase 

 by a quantity, however small ; the balls would then fly out, 

 and as long as the motion was carried on with the same 

 speed, their centrifugal tendency would increase as the interval 

 increased which separated them. 



Let us further suppose them to move with an interval double 

 of that which they keep when in their seats, and so as to make 

 the same number of revolutions in a given time as they did 

 when in their places, — then their tendency to fly out will be 



* Communicated by the Author. 

 Vol.62. No. 306. Oct. 1823. P p double, 



