Maxwell's Theory of the Viscosity of Solicit 



183 



ferent liquids should be constant. In the following table are 

 presented the values of a 2 , D, H, and H/D 2 : — 





a 2 . 



D. 



H. 



H/D 2 . 



Water 



1499 

 5-652 

 3697 



8-577 

 6 056 

 7-137 

 6-434 

 6-758 

 5-678 

 4-977 



1-0 



0-7934 



1-482 



1-038 



0-812 



1-148 



0863 



0-782 



0-698 



0-725 



14-99 

 4-484 

 5-479 

 8-903 

 4-918 

 8193 

 5-552 

 5-285 

 3-963 

 3-608 



14-99 

 7-124 

 2-495 



8-263 

 7-458 

 6-217 

 7 455 

 8-642 

 8135 

 6-863 



Ethyl- Alcohol 







Methyl- Alcohol 









Benzine 



Ether 









There is no relation among these values of H/D 2 which 

 permits the conclusion that the functions f(x) for different 

 liquids have the same form or are connected by any simple 

 relation. This result shows further that Gauss's hypothesis 

 is probably in error. We are, therefore, precluded from 

 drawing a conclusion, which would otherwise follow from 

 Gauss's equation for the contact-angle, as to the limits w r ithin 

 which the molecular forces must lie in case the liquid makes 

 with the solid a finite acute contact-angle. 



In conclusion it may be noted that the values of a 2 obtained 

 by the " q" method are probably fairly accurate for the 

 liquids used. As, however, the investigation was not under- 

 taken with the purpose of obtaining these values as physical 

 constants, no especial pains were used to employ liquids which 

 were chemically pure. 



I desire to express my thanks to Mr. Taylor Eeed and Mr. 

 A. H. Scofield, Fellows of the College, for the assistance 

 which they have given me in the observations. 



Physical Laboratory, Princeton College, 

 Princeton, N.J., U.S.A. 



XX. Maxwell's Theory of the Viscosity of Solids and its 

 Physical Verification. By Carl Barus, Assistant Geolo- 

 gist, U.S. G. S* 



1. npHE viscosity of solids has been theoretically discussed 



JL in more or less elaborate memoirs by O. E. Meyer, 



Boltzmann, Neesen, Warburg, Maxwell, and Butcher. Views 



of a distinctly theoretical kind have also been given by 



* Communicated, with the permission of the Director of the U.S. 

 deal Survey, by the Author. 



