chap, xx.] HYDRODYNAMICS. 207 



The specific gravity of human blood is 1-055 



,, ,, blood serum ,, 1-027 



saliva T006 



bile 1-026 



the aqueous 



humour of the 



eye ,, 1'005 



gastric juice 1-005 



,, ,, muscle 1-060 



tendon f , I 1 125 



nerve 1-040 



brain 1-030 



bone 1-975 



brain 1-030 



CHAPTER XX. 



HYDRODYNAMICS FLUIDS IX MOTION. 



Principle 'of Torricelli. Suppose a liquid 

 flowing freely through an opening in the thin wall of 

 a reservoir, by the principle announced by Torricelli, 

 the rate at which the fluid discharges itself is equal to 

 the velocity which would be acquired by a body falling 

 freely through a height equal to the distance between 

 the orifice and the surface of tJie liquid. The law for 

 falling bodies is, that a body falling freely from a 

 position of rest through a certain distance acquires a 

 velocity, determined by the distance it has travelled, 

 the accelerating action of gravity being taken into 



account. The precise formula is v = \/2gh, where v 

 the velocity is equal to the square root of the accelera- 

 tion due to gravity x 2 X the distance fallen. Liquid 

 in a reservoir may be considered then as consisting of 

 a large number of molecules, and the speed with which 

 the molecules pass through an opening in the bottom 

 is the same as they would acquire if they fell from the 

 surface of the liquid straight down through the opening. 



