0. JBarus — Apparent Hysteresis. 107 



mation due to molecular instability is legitimately termed vis- 

 cosity. 



The initial longitudinal magnetization of the wire does two 

 things : it increases its rigidity (see preceding paper, 1. c.) in 

 marked degree, and it decreases its viscosity during the act of 

 magnetization. The subsequent magnetization merely increases 

 rigidity without the accompanying viscous effect. The phe- 

 nomenon now becomes purely elastic. Thus the first magne- 

 tization after any twist has been imparted is the one which 

 reconstructs the magnetic configurations ; the subsequent mag- 

 netizations (to refer to the mechanism of Ewing's theory) 

 merely deflect the set molecular magnets. 



It follows also that with each fresh twist molecular configu- 

 rations are broken down. This is similar to what occurs in 

 cases of the tempering of a glass-hard or hard drawn magnet. 

 The prepondering amount of the magnetization is wiped out 

 by the simultaneous decay of the hardness.* 



Finally, whenever a wire is strained certain groups of mole- 

 cules lag behind the stress : they may be gradually disinte- 

 grated by time (ssecular viscous deformation) ; more rapidly 

 by rise of temperature (viscous deformation) ; or suddenly as 

 in the present instances, by magnetization. It is not necessary 

 to assume that the breakdown is identically the same even 

 apart from time in all these instances. In other examples 

 (tempering, etc.) whereas the decay of hardness wipes out 

 magnetization, the decay of magnetization does not influence 

 temper; but such cases are easily interpreted. 



If we endeavor to follow the figures 7-11, 14-17, after the 

 first magnetization, we encounter a case in which magnetically 

 increased rigidity is to be imparted to a body of simultane- 

 ously decreased viscosity. The wire momentarily contains 

 groups of unstable molecules and is thus in a condition to 

 yield to the mechanical stress (torque) to which it has been 

 subjected. 



If now we consider the system of two wires and imagine 

 these occurrences to be consecutive, the increment of rigidity 

 would produce a deflection in the same direction as the twist, 

 or work would be done by the magnetized wire upon the non- 

 magnetic wire, against the existing torque. The yield of the 

 wire due to the presence of unstable configurations would pro- 

 duce a deflection in the opposite direction to that of the twist ; 

 or work would be done by the non-magnetic wire upon the 

 magnetized wire. After the first magnetization the greater of 

 these effects will supervene. The result is uncertain as to 

 sign. After subsequent magnetizations for the same twist the 



*Barus and Strouhal. Bull. U. S. Geolog. Survey, No. 14, p. 154-5, 1885; cf. 

 Wied. Ann., xx, p. 662, 1883. 



