THE STEAM ENGINE. 



A ring or collar E is placed on the upright spindle, so as to be 

 capable of moving freely upwards and downwards. To this ring- 

 are attached by pivots two short levers, E F, the pivots or joints 

 at E allowing these levers to play upon them. At F these levers 

 are joined by pivots to other levers F G, which cross each other 

 at H, where an axle or pin passes through them, and attaches 

 them to the upright spindle c D. These intersecting levers are 

 capable, however, of playing on this axle or pin H. To the ends 

 G of these levers are attached tAVO heavy balls of metal. The 

 levers F G pass through slits in a metallic arc attached to the 

 upright spindle, so as to be capable of revolving upon it. If the 

 balls are drawn outwards from the vertical axis, it is evident 

 that the ends F of the levers will be drawn down, and therefore 

 the pivots E likewise drawn down. In fact, the angles E F H will 

 become more acute, and the angles F E F more obtuse. By these 

 means the sliding ring E will be drawn down. To this sliding 

 ring E, and immediately above it, is attached a grooved collar., 

 which slides on the vertical spindle upwards and downwards with 

 the ring E. In the grooved collar are inserted the prongs of a 

 fork K, formed at the end of the lever K L, the fulcrum or pivot of 

 the lever being at L. By this arrangement, when the divergence 

 of the balls causes the collar E to be drawn down, the fork K, 

 whose prongs are inserted in the groove of that collar, is likewise 

 drawn down ; and, on the other hand, when by reason of the 

 balls falling towards the vertical spindle, the collar E is raised, 

 the fork K is likewise raised. 



The ascent and descent of the fork K necessarily produce a 

 contrary motion in the other end sr of the lever. This end is 

 connected by a rod, or system of rods, with the end M of the short 

 lever which works the throttle valve T. By such means the 

 motion of the balls, towards or from the vertical spindle, pro- 

 duces in the throttle valve a corresponding motion ; and they are 

 so connected that the divergence of the balls will cause the throttle 

 valve to close, while their descent towards the vertical spindle 

 will cause it to open. 



These arrangements being comprehended, let us suppose that 

 either by reason of a diminished load upon the engine or an 

 increased activity of the boiler, the speed has a tendency to 

 increase. This would impart increased velocity to the grooved 

 wheel A B, which would cause the balls to revolve with an 

 accelerated speed. The centrifugal force which attends their 

 motion would therefore give them a tendency to move from the 

 axle, or to diverge. This would cause, by the means already 

 explained, the throttle valve T to be partially closed, by which 

 the supply of steam from the boiler to the cylinder would be 

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