LINES 



MAP 9 a. 



OF EQUAL VERTICAL CURRENT IN GREAT BRITAIN, 



in 

 Amperes per Square Kilometre. 

 -j- upward, 

 — Dotvnward. 



Full Lines Deriyed from Quadractic Expresdoos for the Whole Country. 

 Dotted Lines Derived from Emperical Expressions for Different Districts, 



Jour. Sc. Coll. Vol. XIV. PI. XCVI.œ 



