2 O. C. CLIFFORD, JR. 
During the past 6 years the study of micro-geomagnetics has pro- 
gressed beyond the limits of early credulity and, with the publica- 
tions of Heiland, Wilson, Barret, Lynton, Spraragen and others, 
many of these problems are nearing solution. Though other geo- 
VERTICAL MAGNETIC INTENSITY 
(I 52) eT 
CONTOUR INTERVAL $0 GAMMA SCALE OF MILES PRODUCING AREA 
° ‘ 2 
—aee 
OC CLIFFORO.R. 

Fic. 1.—Map showing vertical magnetic intensity, 1927. 
physical methods have rightfully supplanted magnetic methods 
throughout most of the Mid-Continent and Gulf Coast areas, mag- 
netometers must still be considered of exploratory value for special- 
ized structural types and for rapid, inexpensive surveys of regional 
character. 
330 
