390 THE SCIENTIFIC PAPERS OF 



pressed air, to supply air for working his tramway locomotive 

 engine. 



In designing this vessel, the writer acted upon the principle 

 that a metal should be employed to resist the bursting pressure, 

 which should combine strength and toughness in the highest 

 degree, and so disposed that its continuity should not be disturbed 

 by any sudden changes in dimensions or by perforations of any 

 kind. The material selected was steel, of such quality as to be 

 capable of resisting a tensile strain of 45 tons per square inch, and 

 of extending from 8 to 10 per cent, before breaking. 



The vessel itself is represented in Figs. 1 and 2, Plate 34. It 

 consists of several cylindrical rings, A, of 40 inch internal diameter 

 and 12 inch depth, rolled out of solid steel ingots in a tyre mill ; 

 and of two hemispherical ends B beaten out of steel boiler plate. 

 The hemispherical ends and the rings are strengthened at the 

 edges by projecting dwarf flanges, as shown in Fig. 3, and full size 

 in Fig. 4. The only tooling necessary to these rings and ends 

 consists in turning a V groove in each face, Fig. 4, care being 

 taken that all the grooves should be at the same distance from the 

 centre, irrespective of the precise diameter of the several rings A. 

 Packing rings of well annealed copper wire of -^ i ncn thickness 

 were prepared, the diameter of these rings being precisely the 

 same as that of the V grooves, so that the packing rings should 

 lie true in the grooves, as shown in Fig. 4. Two rings C of cast 

 steel, each perforated with twenty holes of 1-f inch diameter, fit 

 over the hemispherical ends, but rest chiefly against their pro- 

 jecting dwarf flanges, as shown in Fig. 3 ; through these holes are 

 passed twenty steel bolts D of lj inch diameter, of such quality 

 as to resist 50 tons per square inch, care being taken to enlarge 

 the screwed ends of the bolts, in order not to weaken their total 

 strength in the ends, but to allow of uniform elastic action 

 throughout their length. 



The different parts composing this vessel having been thus 

 prepared, the vessel was built up as represented in Fig. 1, Plate 34, 

 and the bolts were gradually tightened up to a point just sufficient 

 to resist the intended internal pressure. This being accomplished, 

 the vessel was filled with water, and the pressure of a hydraulic 

 accumulator loaded to 1000 Ib. per square inch was applied. No 

 sign of leakage was observed except at one joint, where the thick- 



