12 W. P. JENNY 
results which we would obtain with torsion balances, if their accuracy 
were reduced to +10 Eétvos. If, however, the accuracy of the mag- 
netometer surveys is greatly increased, these surveys may yield im- 
portant information about structure at commercial depths also in 
these areas where the magnetic anomalies as located by the average 
magnetometer survey are unquestionably due to deeply buried re- 
gional structure." 
As the vectors are of sufficient accuracy, they allow a checking and 
tying-in of scattered magnetometer surveys. These stations should 
prove of the same value to 3-dimensional magnetometer surveys as 
pendulum stations to gravimetric surveys. 
The vector maps show at a glance which areas are of interest for 
magnetometer surveys, what size anomalies may be expected, how 
far a magnetometer survey has to be extended or where it is best 
commenced to cover a certain anomaly. - 
In the following study of the vector maps no attempt has been 
made for an exhaustive interpretation of all vectors. The reader may 
easily perceive an abundance of further detailed information, which 
may interest him, especially in connection with scattered magnetom- 
eter surveys and detailed geologic information. 
LOUISIANA? 
The vector map of this state (Fig. 2) gives a true picture of the 
known main structural trends and further indicates many distinct 
“structures.” 
Sabine uplift—The horizontal components of the two negative 
vectors at Benton and Shreveport concur at a point about 1o miles 
southwest of Shreveport, at which point therefore a magnetic “‘high” 
is suggested. A line connecting this ‘‘high”’ with the ‘“‘high” indicated 
a few miles south of Many coincides well with the axis of the Sabine 
uplift. 
North Louisiana geosyncline—The north Louisiana geosyncline 
is expressed by the negative vectors at Ruston, Jonesboro, and 
Winnfield. 
1D. M. Collingwood, “Magnetics and Geology of Yoast Field, Bastrop County, 
Texas,” Bull. Amer. Assoc. Petrol. Geol., Vol. 14, No. 9 (September, 1930), pp. 1191-97. 
E. D. Lynton, “Some Results of Magnetometer Surveys in California,”’ Bul, Amer. 
Assoc. Petrol. Geol., Vol. 15, No. 11 (November, 1931), pp. 1351-70. 
A. Nippoldt, Verwertung magnetischer Messungen zur Mutung (Berlin, 1930), p. 58. 
2 The local magnetic vectors are based on the information given in “United States 
Magnetic Tables and Magnetic Charts for 1925,” op. cit. 
340 
