392 THE SCIENTIFIC PAPERS OF 



hydraulic, pressure. Taking, for instance, a hydraulic cylinder of 

 2 feet diameter, and an internal working pressure of 2 tons per 

 square inch, the rings have to be rolled of a thickness of 1*6 inch, 

 which corresponds to a working strain of 15 tons per square inch, 

 or one-third of the breaking strain of the material composing the 

 rings. This press would give a hydraulic pressure of 904 tons 

 total, and would weigh probably not more than one-fourth of a 

 press of the ordinary construction. The same argument would 

 apply to accumulators of large dimensions, which could be built 

 up of rings at a comparatively cheap rate, and of practically 

 unlimited range. 



In Figs. 6 to 8, Plate 35, is represented the application of 

 this mode of construction to marine boilers. These boilers are 

 necessarily of large diameter, and in constructing them, of wrought 

 iron, or even of mild steel, plates exceeding 1 inch in thickness 

 have to be employed, and it is not easy to work and rivet plates of 

 such thickness, nor is the riveted seam nearly as reliable as that 

 of thinner plates. In Figs. 6 and 7 is represented a boiler shell of 

 10 feet diameter, of the proposed construction. It consists of 

 twelve continuous rings, of inch thickness of metal, fastened 

 together by sixty-four steel bolts of 1 T V inch diameter, which pass 

 through the end plates, as shown in Fig. 8, and thus bind the 

 whole fabric together. The front end plate is fitted with furnaces 

 and steam tubes in the usual manner. A boiler of this con- 

 struction and of these dimensions could be safely tested up to 

 200 Ib. per square inch, the rings being sufficiently strong to 

 withstand an internal pressure of 600 Ib. per square inch ; and it 

 possesses, in common with the air vessel already described, the 

 advantage of leaking, through the yielding of the elastic bolts, 

 long before there is the least danger of explosion. It possesses 

 moreover the additional advantage that it can be carried in pieces 

 to be put together in sitd, thus facilitating carriage and avoiding 

 the necessity of providing hatchways of extraordinary dimensions 

 for putting the boilers on board. 



In order to prevent galvanic action between the copper and steel 

 rings, it will be found desirable to caulk the joints from within the 

 boiler with india-rubber or with string saturated with some resin- 

 ous compound, or simply to brush such a compound into the joints 

 from within the boiler. 



