﻿Barus and Stirouhal — Viscosity of Steel. 445 



bulk of our knowledge of to-day. A new method of research 

 was indicated by Sir William Thomson,* which method was 

 developed, independently of Thomson we believe, by Streintzf 

 and by Schmidt.:): Thomson § concisely defined the terms now 

 in English use. 



Plan of research. — We purposed at first to study the viscosity 

 of steel from two distinct stand-points: one part of our work 

 was to consider viscosity in its relations to temperature ; the 

 other part, viscosity in its relations to hardness. Indeed we 

 have as yet no data of this kind for steel, at all. For other sub- 

 stances Kohlrausch| and after him Streintz^f and Pisati** had 

 already studied viscosity and temperature with some detail 

 though in a direction differing somewhat from our own. Very 

 recently, however, Schroederf-f of Freiburg has experimented in 

 a line of research quite identical with the one upon which we 

 had determined; and though his data do not include steel, the 

 results obtained for other metals are sufficiently pronounced to 

 make a special investigation of steel superfluous, at least so far 

 as regards its present bearing on our work. Schroeder^ finds 

 u Der bei 100° begonnene Yerlauf der Nachwirkung wird 

 durch abkiihlung des Drahtes auf Zimmertemperatur unter- 

 brochen ; nach erneuter Erwarmung auf 100° wird die vorher 

 unterbrochene Drehung fortgesetzt." We pointed out§§ that 

 in case of drawn metals, of quenched glass (Rupert's drops) and 

 we inferred also in case of tempered steel, energy has been 

 stored up in virtue of the rigidity of the material ; and that on 

 exposure to temperature (annealing), the available excess of 

 stress is made to produce the observed viscous deformation pre- 

 cisely in the way in which Schroeder has found it for applied 

 torsional stress. 



*Sir William Thomson: Phil. Mag. (IV), xxx, p. 63, 1865. Thomson refers the 

 loss of energy of vibration to the existence of molecular friction. 



fStreintz: Pogg. Ann., cliii, p. 387, 1874; Wien. Ber., lxix, part 2d, p. 355, 

 1874. Using a vibration method the author discusses elaborately the effect of 

 viscosity on the logarithmic decrement. 



^Schmidt: Wied. Ann., ii, pp. 48, 241, 1877, supplements Thomson's and 

 Streintz's results, and is able to express logarithmic decrement in terms of time 

 by Weber's formula of three constants. We may add Cohn (Wied. Ann., vi, p. 

 403, 1879), Hopkinson (Phil. Trails. 1877), Warburg (Wied. Ann., xiii, p. 141, 

 1881), Auerbach (Wied. Ann., xiv, p. 308, 1881), Kohlrausch (Pogg. Ann., cxxviii, 

 1886), Ewing (Phil. Trans., p. 545. 1885) and others who discuss viscosity as mani- 

 festing itself in phenomena of conductivity (Cohn), residual static charge (Hop- 

 kinson, Kohlrausch), magnetism (Auerbach, Warburg, Ewing and others). 



§ Thomson : 1. c. 



|| Kohlrausch : Pogg. Ann., cxxviii, p. 216, 1866; ibid, clviii, p. 371, 1876. 



fStreintz; Wien. Ber. lxix, p. 337, 1874; also Schmidt, 1. c. 



**Pisati: Wien. Ber., lxxx, p. 427, 1879. Also Gaz. Chim.Ital., 1876, 1877. 



ft Schroeder: Wied. Ann., xxviii, p. 369, 1876. \\ Schroeder: 1. c, p. 388. 



§§Bull. U. S. G-. S., No. 14, p. 196, 1885; this Journal, xxxi, p. 452, 1866. 



Am. Jour. Sci. — Third Series, Vol. XXXII, No. 191. — December, 1886. 



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