Coefficient of Viscosity of a Liquid. 413 



have shown above ought, if we follow Hagenbach in his 

 assumptions, to be substituted for it. Grartenmeister gave no 

 indications of the method by which this result was obtained, 

 nor of the reasons which rendered it preferable; but stated that 

 a paper by Prof. Finkener on the whole subject would shortly 

 appear. Under the circumstances, therefore, it seemed best to 

 wait for the results which he has obtained before trying to 

 proceed with the question. 



Another attempt to apply to the numbers obtained by 

 Poiseuille in his second series of experiments a correction 

 for the kinetic energy given to the fluid was made by 

 Osborne Reynolds, apparently in ignorance of Hagenbach' s 

 work on the subject, in the paper already referred to (Phil. 

 Trans. 1883). The correction which he employed was 



P505 -K-, and was thus slightly smaller than Hagenbach's, 



whose value was *7937 — . The authority for this correction 



appears to be Weisbach ; but as the experiments from which 

 he deduced it were made with tubes 1 to 4 centim. in dia- 

 meter and only 3 to 12 centim. long, and the head of water used 

 varied from 9 to 24 inches, it is clear that the velocities were 

 so far above the critical velocity as to make the results inap- 

 plicable to this case. Indeed, Weisbach mentions that expe- 

 riments with narrower tubes were found to give a different 

 result. 



Osborne Reynolds considered that when the above correc- 

 tion was applied, Poiseuille's results became consistent ; but 



the correction — gives rather better results in all the experi- 

 ments of the second series which I have examined, while the 

 discordances which any of these corrections introduce among 

 the seeming agreements of the first series are not sufficiently 

 different to help us in deciding between them. 



The subjoined Table gives specimens of the results obtained. 

 It indicates the relative merits of the various corrections, and 

 at the same time shows the inapplicability of the numbers 

 obtained by Poiseuille to the method of calculation suggested 

 in this paper. 



