198 C. Bar us — Viscosity of Solids. 



suits of table 2, as well as in earlier work* in a way so pro- 

 nounced as to be irrefragable. 



If glass-hard steel is annealed at 100°, the greater number 

 of the unstable configurations are broken up in virtue of the 

 increased molecular vibration at the higher temperature. The 

 cold rod, after annealing, will show increased viscosity in pro- 

 portion as the number of unstable configurations has decreased. 

 Experiment proves this in a strikingly conclusive way : the in- 

 crease of viscosity thus produced is marked, being nearly half 

 the difference between the soft and hard states of steel. This, 

 too, is an observation favorable to Maxwell's theory ; for if 

 there be configurations with an inherent tendency to collapse 

 at ordinary temperatures, but a small fraction of them will sur- 

 vive at 100°. Moreover the configurations broken up cannot 

 be reconstructed without expenditure of fresh energy (quench- 

 ing). Since no such energy is ordinarily available, the viscous 

 properties of the annealed rod are of a permanent kind. 



Again if glass-hard steel (or steel annealed at 100°) be soft- 

 ened by annealing at 200°, a greater number of unstable groups 

 will be broken up than in the foregoing case. The viscosity 

 of the cold rod must therefore be considerably greater than 

 that of the hard rod. Experiment proves the viscous increase 

 to be about two-thirds of the whole viscous difference between 

 hard and soft steel. Analysis gives evidence of the occurrence 

 of decomposition ; and inasmuch as the unstable groups are 

 permanently broken, the annealed rod shows determinate vis- 

 cous properties. 



If glass-hard steel be annealed at 300°, 400°, 500°, etc., effects 

 of the same nature as those just discussed, but differing from 

 them in the degree of thorough removal of the unstable con- 

 figurations, will result. 



The phenomenon as a whole must be considered continuous, 

 both as regards temperature and time. In proportion as tem- 

 perature is higher, however. Maxwell's theory predicts that the 

 effects of the same increment of the temperature of annealing, 

 will produce increments of viscosity successively diminishing 

 at a very rapid rate. Supposing molecular configurations 

 originally present in all states of stability, it follows at once 

 that the groups which retain this quality after annealing must 

 very soon vanish when the temperature of annealing is in- 

 creased. The data prove this in a convincing way: Rods an- 

 nealed at 300°, 400°, 500° 1000°, show about the same 



viscous behavior (relatively speaking), notwithstanding the fact 

 that chemical analysis proves that the decomposition incident 

 to the successive application of these temperatures on glass- 



* B. and S. : This Journal, xxxiii, pp. 25, 26, 1887. 



