ITS C. Barus — Effect of Magnetisation on the 



effect of magnetization is here a decrement of viscosity. In 

 the second part the wires for open circuit are equally viscous; 

 for closed circuit the results are the same as in part first both 

 as regards sign and amount. The apparent effect of magnetiza- 

 tion is again a decrement of viscosit}^. Part third, finally, con- 

 tains the interpretation of these results: it is seen that results 

 of the same magnitude and character are obtained when the 

 magnetic field due to the helix (other effects remaining the 

 same) is zero. The viscous effects here observed are therefore 

 wholly due to temperature, and it may be safely inferred that 

 magnetized and unmagnetized steel differ in viscosity by an 

 amount less than is produced by 5° difference of temperature. 



Table 1. 

 Viscosity of steel, annealed 360°. Z=30 cm ; 2/}=0083 cm ; i / =20°. 



h 



0xlO 6 



t 



Remarks. 



h 



<£xl0 6 



t 



Remarks. 



hours. 



o-oo 



2-67 . 

 4-33 



24-00 

 25-42 

 25-60 

 25-67 

 25-83 



radians. 



— 

 -33 



— 35 

 -50 



— 50 

 -35 

 -15 



— 3 

 + 7 

 + 10 

 + 15 



°C. 



1 



Circuit 

 y open. 



r=+6°. 

 J 



Circuit 

 closed. 



7= +6°. 



hours. 

 1-10 

 1-12 

 140 

 1-67 

 1-92 

 2-08 

 2-40 

 2-80 



radians. 

 -21 

 -10 



— 23 



— 23 

 -34 

 -38 



— 42 

 -49 



°C. 



19 

 23 

 25 



27 



28 

 29 



1 



Circuit 



}- closed. 



T= — 6°, 



J 



26-00 

 26-25 



26-75 



o-oo 



0-18 

 0-43 

 0-60 

 0-85 

 1-00 

 4-52 

 23-25 



— 

 -30 

 -46 

 -53 



-58 

 -63 



— 7 

 -17 



17 

 21 

 26 

 28 

 29 

 30 



1 



Circuit 

 i closed ; 

 1 field zero. 

 | r=-6°. 



J 



\ Circ't open. 



j r=-6°. 



o-oo 



1-00 



— 



— 3 



-- 



) Circ't open. 

 | r=-6°. 



Inasmuch as the steel wire of table 1st is permanently a 

 magnet after the first induction, sharper results may be looked 

 for in experimenting with iron. As regards viscosity, iron is 

 less susceptible to the influence of temperature than either an- 

 nealed steel or even soft steel ; it is more magnetically permeable 

 and it loses its magnetization completely when slightly jarred 

 in a zero field. 



Table 2 contains results for soft iron. The arrangement 

 being identical in plan with table 1. 



In the first part of table 2, <p increases whenever both wires 

 are unmagnetic and decreases at a gradually diminishing rate 

 whenever the upper wire is magnetic. The apparent effect of 

 magnetization is therefore a diminution of viscosity, a result in 

 accordance with the inferences from table 1. To interpret this 

 apparent result the second part of table 2 is available. It 



