114 



GENERAL SCIENCE 



be added to every square inch of surface in the vessel. 

 If the inside area of the vessel be 16 square inches,, the 

 extra force exerted will be one pound. 



The Hydraulic Press. It is obvious that a piston 

 may be used instead of water in the above illustration , 



FIG. 104. Hydraulic Press. 



and this means is commonly used to secure the applica- 

 tion of great pressure at a given place. Such a machine 

 is called the hydraulic press. This machine consists of 

 two communicating cylinders each fitted with a piston. 

 One cylinder is usually much larger than the other (Figure 

 104). If the areas of the pistons are in the ratio of one 



