s its
continuation, as shown by the emphasized ridges in figure 13.

Sometimes type lines may be very short. Care must be exercised in
their location. Notice the right type line in figure 14.

When locating type lines it is necessary to keep in mind the
distinction between a divergence and a bifurcation (fig. 15).

_A bifurcation is the forking or dividing of one line into two or more
branches._

_A divergence is the spreading apart of two lines which have been
running parallel or nearly parallel._

According to the narrow meaning of the words in fingerprint parlance,
a single ridge may bifurcate, but it may not be said to diverge.
Therefore, with one exception, the two forks of a bifurcation may
never constitute type lines. The exception is when the forks run
parallel after bifurcating and then diverge. In such a case the two
forks become the two innermost ridges required by the definition. In
illustration 16, the ridges marked "A--A" are type lines even though
they proceed from a bifurcation. In figure 17, however, the ridges
A--A are not the type lines because the forks of the bifurcation do
not run parallel with each other. Instead, the ridges marked "T" are
the type lines.

Angles are never formed by a single ridge but by the abutting of one
ridge against another. Therefore, an angular formation cannot be used
as a type line. In figure 18, ridges A and B join at an angle. Ridge B
does not run parallel with ridge D; ridge A does not diverge. Ridges C
and D, therefore, are the type lines.

_Focal points_--Within the pattern areas of loops and whorls are
enclosed the focal points which are used to classify them. These
points are called delta and core.

_The delta is that point on a ridge at or in front of and nearest the
center of the divergence of the type lines._

It may be:

- A bifurcation

- An abrupt ending ridge

- A dot

- A short ridge

- A meeting of two ridges

- A point on the first recurving ridge located nearest to
the center and in front of the divergence of the type lines.

The concept of the delta may perhaps be clarified by further
exposition. Webster furnishes the following definition: "(1) Delta is
the name of the fourth letter of the Greek alphabet (equivalent to
the English D) from the Phoenician name for the corresponding letter.
The Greeks called the alluvial deposit at the mouth of the Nile, from
its shape, the Delta of the Nile. (2) A