354 



Absolute Viscosity of Solids and Liquids. 



The general explanation of these results has been indicated 

 in § 11. In a liquid or a viscous fluid under moderate stress 

 the instabilities are supplied by the mere thermal agitation at 

 ordinary temperatures, at the same rate in which they are 

 used in promoting viscous motion. Hence viscosity is con- 

 stant at a given temperature. In a solid under stress the 

 instabilities are expended at a rate decidedly greater than the 

 small rate of continuous supply. Thus viscosity decidedly in- 

 increases with time. Suppose, therefore, a solid of initially 

 greater viscosity starts on its viscous deformation at an instant 

 when the viscosity of a solid of initially smaller viscosity has 

 been increased by time to the initial value of the former case. 

 This can actually be realized by twisting a soft steel rod about 

 an hour later than a hard steel rod (tig. 3). Then, in suc- 

 ceeding times, even though the substances start at a state 

 where both are equally viscous, the viscosity of the initially 

 more solid body will rapidly overtake the other ; for the 

 supply of instability due to temperature alone is continuously 

 greater in one case than in the other. 



18. Summarizing the results of the above paragraphs, the 

 viscosities of the three states of aggregation may be expressed 

 in terms of the absolute gjcs scale as follows : — 



Table IX. — Viscosity, considered in its Variations with the 

 State of Aggregation. 



Gases and Vapours. 



; Andrews's 

 critical state. 



J Liquids. 



Substance. 



?. 



Sub- 

 stance. 



V- 



Substance. 



n> 



* Ether, 

 *H 2 , 



* Air, 



to 2 , 



6-8 xl0~ 5 

 8-7 Xl0~ 5 

 1-75 xlO" 4 

 2-12X10" 4 



10~ 5 to ? 



? 

 ? 



? 



to? 



Ether, 30... 

 Ether, 10... 

 Water, 97... 

 Water, 20... 

 § Glycerine... 

 Range 



9xl0~ 4 

 l-9xl0~ 3 

 3-0 xlO" 3 

 1-OxlO" 2 



5 

 ? to 10~ 2 





* Puluj, I c. t O. E. Meyer, I c. p. 142. 



I Landolt and Boernstein's Tables, I. c, and Slotte, I. c. 

 § A rough measurement of my ow 

 161, p. 373, refer to dilute glycerine. 



§ 5a. Graham's results, ' Phil. Trans.' 



