160 The Earl of Berkeley and Dr. Burton on a 



to reciprocate the lever by means of a wire rope, a sufficient 

 weight was hung on to it, and the rope was carried up to a 

 ball-bearing crank-pin, set in the face of a worm-wheel. The 

 worm is driven through a magnetic clutch, by means o£ 

 which the automatic control of the pumping is effected 

 whichever of the three gauges Gr 1? Gr 2 , Gr 3 is in use; the fall 

 of the gauge-piston below a certain level closes the circuit of 

 the electromagnet and causes the pump to work ; the rise o£ 

 the piston above a slightly higher level breaks the circuit 

 and stops the pumping. 



Fig. 6. 



SECTION THROUGH A.B 



The (continuously-driven) pulley on the worm-spindle 



^provides a choice of speeds, the aim being to arrange 



matters so that even with the greatest expected leak only 



intermittent pumping will be needed to keep up the pressure. 



.A detail of the contact-maker is shown in fig. 6. 



