Coefficient of Viscosity of a Liquid. 



409 



rection became at all sensible, and he accounted for this by 

 supposing that the flow in the tube became turbulent at the 

 higher velocities ; but this could not have been the case, as 

 the mean velocity was, in every experiment except the last 

 one, well below the critical value at which linear motion 

 ceases to be resumed upon disturbance. If instead of his 

 correction we use the modified form which we have shown 

 should replace it, the results are distinctly better, as will be 

 seen from the subjoined Table, which gives the values in 

 C.G.S. units of the coefficient of viscosity of water deduced 

 from Hagenbach's experiments. 



Employing 

 Hagenbach's 

 correction. 



Einplojdng the 

 larger correction. 



Temperature. 



•0101 



•0101 



o 

 197 



•0101 



•0100 



19-7 



•0100 



•0099 



19-7 



•0093 



•0092 



20-2 



•0098 



•0098 



204 



•0099 



■0098 



20-2 



•0101 



•0100 



19-8 



•0101 



•0099 



20-1 



•0101 



•0100 



196 



0103 



•0100 



19-6 



0104 



•0100 



19-5 



•0110 



•0105 



19-7 



•0118 



•0110 



19-7 



•0118 



•0106 



19-5 



•0126 



•0109 



196 



■0138 



•0109 



19-5 



Hagenbach also applied his correction to a number of ex- 

 periments of Poiseuille's. We shall see later that here also it 

 gives in its modified form results which are slightly less 

 inconsistent. 



It is clear, however, that in the application of this method 

 of treatment to experiments such as those considered above 

 we tacitly assume, in calculating the value of h, that the 

 pressure over the whole of that end of the tube from which 

 the liquid issues may be taken as sensibly constant and of the 

 same value as if there were no motion ; an assumption 

 unsupported by probability. 



The complete discussion of the problem before us is impos- 

 sible in the absence of a solution for this case of the equations 

 of motion of a viscous fluid, but some considerations upon 



