THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



NOVEMBER 1888. 



XLIV. The Secular Annealing of Cold Hard Steel. 

 By Carl Barus*. 



INASMUCH as the method I used for testing Maxwell's 

 theory of the viscosity of solids contains a proof of that 

 theory a fortiori, I did not distinguish in my last paperf be- 

 tween a break-up of configurations of molecular wholes and the 

 more intensified break-up in which the integrity of the molecule 

 itself is invaded. The experimental distinction is not always 

 easy. If, for instance, I dissolve certain solids (pitch, say, in 

 turpentine) I may produce a continuous series of viscous 

 fluids ; but the molecular mechanism by which this is brought 

 about cannot in the present state of our knowledge of solution 

 be said to be known. I may cite another striking example — 

 ebonite, which above 100° loses viscosity at an exceedingly 

 rapid rate by mere heating ; but, again, the molecular change 

 which produces the viscous effect is obscure. And so gene- 

 rally in less remarkable experiments J. In the case of metals, 

 it appears that those elements whose molecules are least stable 

 and possibly monatomic§ (K, Na, <fcc.) are of a soapy con- 

 sistency, so that here viscosity (" Nachwirkung ") and perma- 

 nent set can hardly be distinguished. In general it appears 

 that metallic permanent set is physical manifestation of loose- 

 of molecular structure. If, as in the case of annealing 

 glass-hard steel, the rigid arch (say) of molecular wholes 

 breaks up because one or more of the molecules, the stones of 



* Communicated by the Author, 

 t This Magazine, August 1888. 



X Cf. Loth'ar Meyer (Die modernen Theorien der Chcmie, Breslau, 

 1884, chapter viii.), on solid molecular structure. 

 § Ibid, chapter, xvi. § 308, &c. 



Phil. Mag. S. 5. Vol. 26. No. 162. Nov. 1888. 2 E 



