PART II. 



HYDRODYNAMICS.* 



Hydrostatic st treats of the weight and pressure of 

 liquids when not in motion ; Hydraulics,1: of liquids in 

 motion, as, conducting water through pipes, raising it 

 by pumps, &c. ; and Hydrodynamics includes both, by 

 treating of the forces of the liquids, whether at rest or 

 in motion. 



CHAPTER I. 



HYDROSTATIC 



SECTION I. 

 UPWARD PRESSURE. 



A REMARKABLE property of liquids is their pressure 

 in all directions. If we place a solid body, as a stone, 

 in a vessel, its weight will only press upon the bottom ; 

 but if we pom- in water, the water will not only press 

 upon the bottom, but against the sides. For, bore a 

 hole into the side, and the side pressure will drive out 

 the water in a stream; or, bore small holes into the 

 sides and bottom of a tight wooden box, stopping them 



* From two Greek words, hudor, water, and dunamis, power, 

 t From two Greek words, hudor, water, and statos, standing, or at 

 rest. t From two Greek words, hudor, water, and aulas, a pipe. 



