PRESSURE UPON THE BASE OF VESSELS. 



165 



/essel, let fig. 114 represent a vessel with vertical sides, 

 which has been placed empty in one scale-pan of a 

 balance and counterpoised by weights placed in the 

 Dther scale-pan. It is evident that if 100 gr of water 

 oe now poured into the vessel, weights amounting to 

 [00 grammes will have to be placed in the opposite 

 scale-pan, in order to restore equilibrium ; this will hold 

 rood, whatever be the weight of the liquid which is 

 >oured into the vessel an equal weight must always be 

 )laced in the opposite scale-pan to produce equilibrium. 

 ?or although the liquid presses not only on the bottom 

 >f the vessel, but also against the sides, so that if 

 hey were moveable it would force them outwards, still 



FIG. 1M (l real size"). 



FIG. 115. 



IS 



he total horizontal pressure upon any one side 

 neutralised by an equal and contrary pressure upon the 

 jpposite side; for although the pressure increases with 

 |be depth (as indicated by the arrows in the figure), it 

 ' the same at all points of each horizontal layer, 

 ilence the only pressure that can take effect externally 

 * the downward pressure upon the bottom of the vessel, 

 nd therefore, in a vessel with perpendicular sides the 

 ressure upon the base is equal to the weight of the con- 

 lined liquid. 



