MAGNETIC VECTOR STUDY IN OIL STATES 9 
local magnetic vectors as due to the local “‘structures” only, after the 
normal magnetic field of the earth has been eliminated. The total 
local vector is shown to be resolvable into two components—the local 
vertical and the local horizontal magnetic vector. 
We have assumed that the material of the anticlines is of more 
than average magnetic permeability and the material of the syncline 
of less. Thus the magnetic ‘“‘high”’ corresponds with a structural 
“high,” and the magnetic “‘low”’ with a structural “low.”’ This is the 
ordinary condition, for example, if two granite ridges are embedded 
in shales and limestones. Should the material of the anticlines be of 
less than average magnetic permeability and the material of the 
syncline of more, then the shape of the magnetic lines of force remains 
the same, but their direction is opposite to the direction shown in the 
picture. Thus a magnetic “‘low”’ would correspond with a structural 
“high” and vice versa. This condition exists in many places, for ex- 
ample in Kansas, where granite plugs or ridges pierce through the 
overlying highly magnetic schists. 
For a clearer understanding, let it be assumed that the magnetic 
effects of the two anticlines and the syncline are equivalent to the 
effects of two negative (—P) poles, and one positive (+P) pole, as 
shown in Figure r. 
Above the negative poles the magnetic intensity is directed per- 
pendicularly downward toward the poles (positive vector). Above the 
positive pole the magnetic intensity is directed perpendicularly up- 
ward, away from the pole (negative vector). Along the surface, half 
way between the positive and negative poles, the two vertical tenden- 
cies compensate each other and only a horizontal component remains, 
directed from the positive toward the negative pole (neutral vector). 
Between the vertical and horizontal directions of the intensity there 
occurs a gradual change, as shown in the picture. As long as the vector 
is still directed downward, it may be called a positive vector; if the 
direction is upward, a negative vector. 
It might happen now that stations I and III had been occupied 
by the Coast and Geodetic Survey. As both stations have the same 
magnetic vertical intensity they lie on the same isogam, which would 
pass over the entire structure without taking the slightest notice of it. 
The same would happen, if also stations III and IX had been sur- 
veyed. Any other combination of the vertical intensity of two or 
three stations give widely varying indications of some anomaly. We 
should consider, however, that most of the “‘structures,”” which create 
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