4 O.C. CLIFFORD, JR. 
on closer scrutiny. The dominant featute of the later survey, also, is 
an area of negative relief, but this has been shifted from the west half 
of Sec. 12, T. 11 N., R. 3 W., to the SE. 14 of Sec. 10, T. 11 N., R. 
3 W. The maximum closure appears to be approximately the same, 
VERTICAL MAGNETIC INTENSITY 

Fic. 2.—Map showing vertical magnetic intensity, 1932. 
though it may be greater in the later work. In the recent survey, the 
contours lie closer together and the general pattern practically dupli- 
cates that of 1927, but the plane of the feature appears to have been 
tilted toward the west. 
The base point, SE. corner, Sec. 36, T. 11 N., R. 3 W., is identical 
332 
