Fluid Discharges as affected by Resistance to Flow. 287 



as 075 * have been obtained. The curves of fig. 1 showing 

 against V are typical of such results, each curve ten ding- 

 to either high or low values of G, for low heads. 



Ficr. 1. 



80 120 S60 200 240 



head fin feet of water) 



Resistance to fluid motion may be written f 



:b-p-{a3+k} 



or = av 2 + bv 2 , 



(3) 



are constants. Generally, the value 

 of " a " is positive, but cases occur frequently { in which 

 it is found to have a negative value. The presence of 

 this negative coefficient is undoubtedly difficult to explain. 

 but leaving any such explanation aside for the present, it 



* Ilerschel, Trans. Am. Soc. C.E. vol. xvii. p. 228. See also Gibson. 

 loc. cit. 



t Advisory Committee Aeronautics, 1910-1 1. 



X Ibid. See also Villamil, ' Motion of Liquids/ p. 178. 



