EuTHERFOBD. — On Magnetic Viscosity. 



189 



results. It also shows that the time-intervals theoretically 

 calculated are the true intervals, and that successive turns 

 of the screNY correspond very accurately to equal intervals 

 of time. 



Table for Curves 1. 



(Dotted curve is the theoretical curve, and the other the experimental 



curve.) 



In the experiments on magnetic viscosity rings of soft iron 

 and steel were taken, and the times of rise of the magnetizing 

 current determined as explained previously. 



Particulars of Soft-iron Ring. 



Composed of iron wire O'OOSin. in diameter, wound into a 

 ring and thoroughly insulated from eddy currents by shellac 

 varnish. 



Mean diameter of ring, 8cm. 



Sectional area of ring, 0-079 sq. cm. 



Wound with three sets of coils of 511 turns altogether. 



The magnetizing force corresponding to one ampere of cur- 

 rent round the ring was 25-5 C.G.S. units. 



Partictdars of Steel Ring. 



Composed of fine steel wire Q-Olin. in diameter, insulated 

 with shellac varnish. 



Mean diameter, 8'3cm. 



Sectional area of ring, 0-14 sq. cm. 



Wound with two sets of coils ; total, 365 turns. 



The static hysteresis curve for the soft iron and steel was 

 very accurately determined. A special method was used, 

 vi^hich allowed each individual point in the curve to be deter- 

 mined several times in succession. 



From experiments with the time-apparatus it will be seen 

 that the current i-ose to a maximum in the ring in about 

 ■j^o of ^ second ; so that the secondary current must have 



