154 The Earl of Berkeley and Dr. Burton on a 



construction and working need not be referred to in detail. 

 For raising the pressure rapidly to (say) 600 atmospheres, 

 there is a low-pressure reciprocating plunger operated by a 

 lever and working in conjunction with automatic suction 

 and discharge-valves in the usual way. For the attainment 

 of higher pressures, the low-pressure pump is then shut off 

 by screwing down a needle-valve, and a high-pressure 

 plunger of small section is gradually forced inwards by 

 means of a screw provided with a star-handle. 



The arrangement of pump, tubing, gauges, and valves 

 is shown diagrammatically in plan and elevation in fig. 1. 



Fig. 1. 

 Elevation. 



Plan. 



'The gauges (G l5 G 2 , G 3 ) are of the "dead-weight" type, 

 the essential feature being an accurately cylindrical piston 

 of hardened steel fitting as closely as possible without actual 

 rubbing contact in a mild steel cylinder, so that, whilst 

 the combination forms an almost oil-tight joint, the mecha- 

 nical friction opposing a lengthwise motion of the piston is 



