EXPLANATION OF THE PLATES. 335 



PLATE VIII. 



Fig. 1. represents a section of the steam pipes and valves of Messrs. Fenton 

 and Murray's * double engine, Plate xiv. ; and Fig. 2. the communicating rods. 

 The steam enters by the pipe C, which has a throttle valve at a, to regulate the 

 supply of steam to the engine, (art. 544.) It is regulated by the action of the 

 governor balls on the lever b, by the connecting rod c : the rotary motion is com- 

 municated to the axis of the governor, by means of a band passing from a pulley 

 on the crank shaft to a similar pulley d on the axis of the governor. The governor 

 consists of two bent levers e e, passing through a slit in the middle of the spindle, 

 and turning upon an axis at/. The upper part of the spindle has a slide h, which 

 is connected to the levers by the rods i i, and ascends when the centrifugal force 

 of the governor increases, so as to cause the balls to rise, and descends when it 

 decreases ; and the lever / moves with it, and consequently the valve. When the 

 engine is at rest, the balls jj rest against the arms k k ; the upper end of the 

 levers e e are nearer to each other ; and the rod c is raised so that the throttle 

 valve may be quite in a horizontal direction, and the pipe completely open for the 

 passages of the steam. See art. 550. 



By the pipe D D, the steam passes either to the top or bottom of the cylinder 

 from the throttle valve a, and by the eduction pipe E E the steam from either 

 passes down to the condenser. The valves n o have each a cylindrical tube or 

 spindle passing through the stuffing boxes r s ; the upper end of each of these has 

 a stuffing box, the upper one at t, the other at u, for the rods of the valves p g, 

 which open to the eduction pipe E, so that either the steam or eduction valves may 

 be opened without allowing steam to escape. 



Fig. 2. is a front view of the two sliding rods which give motion to the 

 valves n, o, p, and q. These rods are kept in a perpendicular direction by the 

 pieces z 2, and the guide 1 ; the lower end of the rods have friction rollers 3 3, 

 which are acted upon by the two eccentric pieces 4 4, on the horizontal shaft Z, 

 which derives its motion from a shaft Y, placed at right angles to, and communi- 



* In reference to these nozles and side pipes, Fenton and Murray brought an action against 

 Boulton and Watt for an infringement on their patent for working one valve through the other ; 

 but it was decided that Mr. Boulton's Mint Engine had been working with valves similarly con- 

 structed for a length of time previous to their patent. 



