36 



THE APPLICATIONS OF PHYSICAL FORCES. [BOOK i. 



and replaces it by the introduction of a metallic wire or rope. The 

 wire or rope, which is thus introduced by means of traction into the 

 body of the press, conveys to the incompressible liquid in the latter 

 the force necessary to introduce it, and this pressure is multiplied, as 

 in the common hydraulic press, in the ratio of the sectional area of 

 the large piston and of the wire. But how is the wire introduced ? 



In the body of the press (Fig. 15) is a bobbin worked from the 

 outside by means of a handle ; round this the wire is gradually coiled 

 from another exterior bobbin. By degrees the wire is introduced into 



FIG. 15. MM. Desgofte and Ollivier's " sterhydnmlic " press. 



the liquid (generally oil) which the body of the press contains. The 

 liquid is thus displaced, and the pressure exerted, in order to make 

 room for the displaced liquid, is transmitted equally to every part 

 of the sectional area of the piston equal to the section of the 

 wire. 



In this new arrangement invented by MM. Desgoffe and Ollivier 

 there are two distinct advantages. In the first place, the compressing 

 power is considerably increased, as it is possible to givo, the wire a 

 much smaller diameter than that of .the piston of any possible force 

 pump, on account of the breakage which would inevitably occur in 

 the case of a metal rod, if its dimensions were too small. Secondly, 

 the introduction of the wire in the sterhydraulic press is made 



