Permanent Elongation of Hard-drawn Wires. 

 Table IX. [continued). 



355 



Viscous Fluids. 



Solids. 



Substance. 



V- 



Substance. 



V- 



Marine glue 



2X10 8 

 10 2 to 10 u 



Paraffine at 20° (m.p. \ 

 55°). | 



t Hard steel, glass &c. 

 t Soft steel 



>2xlO u 



r io 17 to 



t 6xl0 17 



J6xl0 17 to 

 \6xl0 18 



10 u to 10 20 



Range 



Range 





i 



t During the first hour (500 to 3000 seconds) after twisting just within the 

 elastic limits, 



The limits here defined are somewhat arbitrary. They will 

 be made more definite when a greater number of substances 

 lying on the boundary between the classes have been examined. 

 Information is lacking and particularly desirable in the 

 neighbourhood of Andrews's critical temperature. From 

 Table IX. it does not seem improbable that the critical tem- 

 perature may be definable by a narrow limit of viscosity, quite 

 apart from the substance operated on. What this limit may 

 be I do not venture to assert, seeing that the viscosity of gases 

 decreases on cooling, whereas that of liquids increases on 

 cooling. 



Table IX. gives the positively astounding range of varia- 

 tion of 97, the chief variable of our material environment — a 

 variable which throughout the whole enormous interval in 

 question nowhere fails to appeal to our senses. 



Phys. Lab., U.S. Geological Survey, 

 Washington, D.C., U.S.A. 



XXXVI. On the Effect of Permanent Elongation on the Cross 

 Section of Hard-drawn Wires. By Professors T. Gray 

 and C. L. Mees*. 



IN the course of a series of experiments on the torsional 

 rigidity of metals, forming part of the course of instruc- 

 tion in elasticity in the mechanical laboratory of the Rose 

 Polytechnic Institute, we were somewhat surprised to find a 



* Read before the Physical Society of Glasgow University, February ilS, 

 1890. Communicated by Th. Shields, M.A., Secretary. 





