contour map and either recorded or put into a calculating machine. These 

 values are given the positive sign if read at the top of the circle and the 

 negative sign if read at the bottom. The contribution to H z of the term con- 

 taining // is computed in the same way except that horizontal rectangles are 

 used. The values read off the map were recorded as follows: 



4.420 



sum 



-1.815 



Using / = .002, n = .866, I = .5,* 4 

 and for the II terms 



•1, 



z s — .1, we get 



2rc/(4.42) {x k - x,) = 2 (.866) (.002) (4.42) (.1) = 153 gammas 

 and for the // terms 



211 ( -1.815) (z a - z x ) = 2(.5) (.002) (-1.815) (.1) =—36 gammas 

 The sum of these two terms yields H z — 117 gammas. 



Vertical Component H ; of Field of Vertical Cylinder 



In this case the coordinate axes are chosen such that the y axis is per- 

 pendicular to the direction of magnetization and as before with the positive z 



605 



