!!'.> 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



In Figure 3 let P and (} be two points on the I vs. If curve fur m,, 

 where ^ has 'I"' "rdinate of the point of inflection ^ , and I* ia any 

 other point of the magnetization curve. Now Bappose the rod were 

 magnetized by an infinite //' to the maximum l r , so that all the 

 -rr/ x lines are straight and enter and leave the rod at the squared-off 

 ends (a being the radius of the rod). In this case the distribution of 

 magnetism which we may consider the cause of the demagnetizing force 

 //,, or A//, is wholly superficial, and as far away from the secondary 

 coil, where / is measured, as possible, and it has a perfectly definite 

 value AZTqo, say, which we lay off on the /vs. (//'—//) plane, getting 

 the point K, and we draw the line OK. We see now that if, as we in- 



FlCl'RE 3. 



Diagram illustrating magnetization and back-shearing curves. 



crease /from zero to I& by continually increasing //', the lines of mag- 

 netization were always straight, then the demagnetizing force would 

 always be proportional to /, no matter what the susceptibility might be, 

 and tin- .V-curve would be the straight line OK. Another case where 

 the iV-curve would be a straight line OK\ would be realized if the sus- 

 ceptibility were a constant for all values of / from to / x . In this 

 case no volume density would appear by magnetization, and any two 

 fields /// and //./, giving separately the surface densities of magnetism 

 o"! and o-o, could be superposed, so that a magnetizing field /// -f IU 

 would give the superficial distribution v\ + tr%. This last supposition 

 would result in there being no limit to the intensity of magnetization. 

 As a matter of fact the / is uniform only for an infinite //'. At the 

 point P, if P is not the origin, more or less lines of induction will leave 



