THE WALL AH AH COLLIERY. 



249 



volts, 360 amp., with 250 r.p.m. and generating- lOOkw. This 

 was driven by one of McE wen's engines rated for 187h.p., 

 supplied with a Begtrup inertia governor (Fig. 158). A long 

 bar called the inertia bar, with weights at each end, is pivoted 

 at the centre on a roller bearing to an arm of the governor 

 wheel. At the centre of the bar is a short extension, which 

 carries the eccentric pin. A heavy coil spring is secured to 

 the middle of one end of the bar, and on the other end is an 



Fig. 157. The Aldrich Electric Pump. 



air dash pot, which consists of a cylinder with a loose-fitting 

 piston, and connecting rod bolted to the inertia bar. The 

 weight in the spring end of the inertia bar is the greater. 

 Owing to the shape and relation of the various parts of the 

 governor, the weighted end is so acted on by centrifugal force 

 as to tend to swing it backwards towards the left hand stop. 

 This tendency to move backwards is counterbalanced by the 

 spring, the tension of which is such as to hold the inertia 



