only at the point where information is desired, obviously possesses 
an inherent advantage over a method which requires a great 
horizontal travel through the bed itself. (See Fig. 1 and 2.). 
ae ep xn 8p RR ge AR BPR 
Fig. 1 Fig. 2 
In areas where correlation of reflecting horizons is imprac- 
ticable over any great distance, this difficulty may be overcome 
by use of the “dip” method, or more detail shooting. The so-called 
dip method is essentially a short distance correlation between 
successive recording points of one shot point (setup indicated by 
two recording positions in Fig. 2). Correlation of reflections can 
easily be established between records obtained from positions thus 
closely spaced, and individual depth calculations may be used to 
determine the slope of the reflecting bed. This slope in turn estab- 
lishes the position of the bed with respect to shot and recording 
points. 
Assuming that depths, and hence slopes, by short distance cor- 
relation, can be determined by the reflection method, the new 
problem by its very nature should lend itself readily to solu- 
tion. This statement is made because of the sloping nature of 
the sediments close to the flank of a dome. Obviously the point 
of reflection from a horizontal bed will lie vertically under a 
point midway between shot and recorder. If, however, this bed 
be sloping, the reflection point will be moved out from the 
vertical and will lie at that point where lines drawn from shot 
and recorder will make equal angles with the normal to the 
bed at the point of reflection. (See Figs. 3 and 4) 
R sP R , 
Fig. 3 Fig. 4 
12 
