ex- 

 are 



352 Mr. C. Barus on the Change of the Order of Absolute 



conditions. In all cases there is gradual molecular change, 

 and the solid finally breaks without any apparent cause. 



17. The chief results of Tables IV. to VII. are the values 

 aft, whether they be regarded as time-functions, or as 

 ponents of the solidity of steel. In fig. 3 these data 

 constructed graphically. An inspection of the figure shows 

 at once that both solid viscosity and its rate of increase with 

 time are magnitudes winch increase together (Tables IV., VI. 

 compared with Tables V., VII.). After about an hour has 

 elapsed since twisting, the viscosity of hard steel may be quite 

 as large as the initial viscosity of soft steel ; but at corre- 

 sponding times the viscosity of soft steel continues to be 

 more and more pronouncedly the greater. 



The curves are not consistent as to curvature. This may 

 be best inferred from the hard wires, where the viscosities 

 are smaller, the deformations large, and the observations there- 

 fore as a whole much more accurate (Tables IV., VI.). 

 Hence I regard the promiscuous irregularities of fig. 3 as due 

 to errors of observation and construction. According to the 

 law of F. Kohlrausch*, — dcf)/dt = a(p/t n , where a and n are 

 constants. In case of small torsions or short times, —dxpjdt 

 = occf>/t suffices. Thus for the purpose of deducing the time- 

 rates, #, of increase of solid viscosity, it is permissible to re- 

 gard the curves of fig. 3 as essentially linear. 



This is done in the following table. 



Table VIII. — Mean time-rate of increase of the absolute 

 Viscosity of Steel, hard and soft. 



Hard Steel. 



Soft Steel. 





Twist No. 



kXIO -12 . 







Twist No. 



icxlO" 12 . 







q cs 2 . 





glcs\ 



Table IT.... 



4 



220 



, Table V.. . 



1 



1200 





— o 



140 





— 2 



1400 





6 



240 





3 



1900 



Table VI... 



1 



230 



> Table TIL 



1 



1500 





2 



140 





-2 

 3 



1200 

 1000 



Mean rate k 





... 194 xlO 12 



Mean rate 



fC 



.. 1400 xlO 12 



Mean viscos 



ity at 500 s 



>c. 140 xlO 15 



Mean "viscosity at 500 se 



c. 570 XlO 15 



Kohlrauscb., P^gg. Ann. cxxviii. p. 216 (I860). 



