610 

 But 



EXPLORATION GEOPHYSICS 



sin P2 — 



y 



\/x^ + y^ 



and 



sin j8i = 



a — y 



Hence 

 Similarly 



2 I g-y 



V^' + y V(c^-y)^ + 



;.r2y 



-f^Rf! — 



7 / a — X X \ 



y \V(a-'^y + y^ ■\/y'' + ^v 



H ^ ^ ( ^ """^ + ^ ^ 



'''' a-^\\/{a-yy+ {a-xY yJ{a-xY + y^) 



"''' a-y\^{a-yy + x^ \/ {a - x)^ + {a- yY J 

 CI B 



M — 



Fig. 381. — Sketch illustrating the geometric relations between the 

 quantities /, a, etc., which enter into the computation of the magnetic 

 field at a point having the coordinates x and y. 



If it is assumed that the current / flows in the direction of the arrow, 

 the fields Hab to //ad in the figure are all directed into the paper (away 

 from the reader). Hence, the resultant field at P is 



// = //ab + Hbo+Hod + Hda. 



