The Science of Fingerprints | Page 6

pattern
area with two or more bifurcations opening toward the core. Figure 28
is an example of this. Ridge A enters the pattern area and bifurcates at
points X and D. The bifurcation at D, which is the closer to the core, is
the delta and conforms to the rule for deltas. A--A and B--B are the
type lines. A bifurcation which does not conform to the definition
should not be considered as a delta irrespective of its distance from the
core.
- The delta may not be located in the middle of a ridge running between
the type lines toward the core, but at the nearer end only.
The location of the delta in this case depends entirely upon the point of
origin of the ridge running between the type lines toward the core. If
the ridge is entirely within the pattern area, the delta is located at the
end nearer the point of divergence of the type lines. Figure 29 is an
example of this kind.
[Illustration: 29]
[Illustration: 30]
If the ridge enters the pattern area from a point below the divergence of
the type lines, however, the delta must be located at the end nearer the
core. Ridge A in figure 30 is of this type.
In figure 31, A--A and B--B are the type lines, with the dot as the delta.

The bifurcations cannot be considered as they do not open toward the
core.
[Illustration: 31]
[Illustration: 32]
In figure 32, the dot cannot be the delta because line D cannot be
considered as a type line. It does not run parallel to type line A--A at
any point. The same reason prevents line E from being a type line. The
end of ridge E is the only possible delta as it is a point on the ridge
nearest to the center of divergence of the type lines. The other type line
is, of course, B--B.
The delta is the point from which to start in ridge counting. In the loop
type pattern the ridges intervening between the delta and the core are
counted. The core is the second of the two focal points.
The core, as the name implies, is the approximate center of the finger
impression. It will be necessary to concern ourselves with the core of
the loop type only. The following rules govern the selection of the core
of a loop:
- The core is placed upon or within the innermost sufficient recurve.
- When the innermost sufficient recurve contains no ending ridge or
rod rising as high as the shoulders of the loop, the core is placed on the
shoulder of the loop farther from the delta.
- When the innermost sufficient recurve contains an uneven number of
rods rising as high as the shoulders, the core is placed upon the end of
the center rod whether it touches the looping ridge or not.
- When the innermost sufficient recurve contains an even number of
rods rising as high as the shoulders, the core is placed upon the end of
the farther one of the two center rods, the two center rods being treated
as though they were connected by a recurving ridge.

The shoulders of a loop are the points at which the recurving ridge
definitely turns inward or curves.
Figures 33 to 38 reflect the focal points of a series of loops. In figure 39,
there are two rods, but the rod marked "A" does not rise as high as the
shoulder line X, so the core is at B.
[Illustration: 33]
[Illustration: 34]
Figures 40 to 45 illustrate the rule that a recurve must have no
appendage abutting upon it at a right angle between the shoulders and
on the outside. If such an appendage is present between the shoulders
of a loop, that loop is considered spoiled and the next loop outside will
be considered to locate the core. In each of the figures, the point C
indicates the core. Appendages will be further explained in the section
concerning loops.
[Illustration: 35]
[Illustration: 36]
[Illustration: 37]
[Illustration: 38]
[Illustration: 39]
[Illustration: 40]
Figures 46 to 48 reflect interlocking loops at the center, while figure 49
has two loops side by side at the center. In all these cases the two loops
are considered as one. In figure 46, when the shoulder line X--X is
drawn it is found to cross exactly at the point of intersection of the two
loops. The two loops are considered one, with one rod, the core being
placed at C. In figure 47, the shoulder line X--X is above the point of
intersection of the two loops. The two are considered as one, with two
rods, the core being at C. In figure 48, the shoulder line X--X is below

the point of intersection