SIR WILLIAM SIEMENS, F.K.S. 391 



f the copper packing ring appeared to have been insufficient 

 to fill the groove. This defect was remedied by passing the edge 

 of a thin chisel in between the flanges, and pressing the copper 

 rini; in that place by gentle hammering, which had the immediate 

 . -flirt of stopping the leakage. The internal pressure was there- 

 upon gradually raised to 1300 Ib. per square inch, at which point 

 nearly all the joints began to weep, showing that a pressure had 

 been reached at which the bolts commenced to elongate. Each 

 nut was thereupon tightened up another eighth of a turn, and the 

 pressure again applied ; when the vessel was found to be perfectly 

 tight at the previous pressure of 1300 Ib. per square inch, but 

 began to show leakiness at all the joints when the pressure reached 

 1400 Ib. On lowering the pressure again to 1300 Ib. per square 

 inch, no further leakage was observed, showing that the joints had 

 been completely closed again by the elastic pressure of the bolts. 



Considering that the intended working pressure of this vessel is 

 ( mly 1 000 Ib. per square inch, it was thought unnecessary to draw 

 the bolts any tighter, although, according to calculation, the 

 rings as well as the bolts are capable of resisting with safety above 

 2000 Ib. per square inch. It was thought safer on the contrary to 

 allow the bolts to be tightened up to such a point only, that, if by 

 any accident the pressure should considerably exceed the ordinary 

 working limit, they would yield by slightly elongating, and would 

 thus act the part of an elastic safety valve in allowing the fluid 

 pressure to escape through the metallic joints. The great length 

 of the bolts ensures a sufficient elastic range of action for this 

 purpose ; and being made of steel containing 0'5 per cent, of 

 carbon, they will retain their elasticity for an indefinite length 

 of time. 



This vessel, which was constructed at the Landore Steel Works, 

 has now been delivered to the makers of the engine, Messrs. 

 Greenwood and Batley of Leeds ; and the engine will shortly be 

 employed at Woolwich Arsenal as an air locomotive for shunting 

 purposes, 



The same principle of construction in the writer's opinion is 

 applicable to hydraulic cylinders and accumulators, as represented 

 in Fig. 5, Plate 34. In this case the longitudinal bolts need 

 only be strong enough to tighten the copper joints, whereas the 

 cylindrical steel rings have to be made strong enough to resist the 



