168 OUTLINES OF NATUEAL PHILOSOPHY. 



HYDROSTATICS. 



SECT. I. 



PRESSURE OF FLUIDS. 



. A FLUID is a body so constituted, that its 

 parts are ready to yield to the action of any pres- 

 pure, however small, in any direction. 



NEWTON, Principia, lib. n. sectio 5. in initio. AR- 

 CHIMEDES de Insidentibus Humido. 



Hydrodynamics is the science which applies the prin- 

 ciples of Dynamics to determine the conditions of 

 motion and rest in fluid bodies, and is divided into 

 four parts, according as fluids are incompressible or 

 elastic, and according as their equilibrium or their 

 motion is considered. 



"\Vhen fluids are incompressible, like water, the sci- 

 ence which explains the laws of their equilibrium is 



called 



