ain arch would be an accidental whorl.

This subclassification also includes those exceedingly unusual
patterns which may not be placed by definition into any other classes.

Figures 269 to 271 are accidentals combining a loop with a tented
arch. Figures 272 to 276 combine a loop and a plain whorl or central
pocket loop. Figure 277 combines a loop and a double loop. Figure 278
combines a loop and a plain arch, so it is classified as a loop.
Figure 279 combines a loop and a tented arch.

[Illustration: 269]

[Illustration: 270]

[Illustration: 271]

[Illustration: 272]

[Illustration: 273]

[Illustration: 274]

[Illustration: 275]

[Illustration: 276]

[Illustration: 277]

Some whorls may be found which contain ridges conforming to more than
one of the whorl subdivisions described. In such cases, the order of
preference (if any practical distinction need be made) should be: (1)
accidental, (2) double loop, (3) central pocket loop, (4) plain whorl.

[Illustration: 278]

[Illustration: 279]

[Illustration: 280]

[Illustration: 281]

_Whorl tracing_

The technique of whorl tracing depends upon the establishment of the
focal points--the deltas. Every whorl has two or more. When the deltas
have been located, the ridge emanating from the lower side or point of
the extreme left delta is traced until the point nearest or opposite
the extreme right delta is reached. The number of ridges intervening
between the tracing ridge and the right delta are then counted. If the
ridge traced passes inside of (above) the right delta, and three or
more ridges intervene between the tracing ridge and the delta, the
tracing is designated as an "inner"--I (fig. 280). If the ridge traced
passes outside (below) the right delta, and three or more ridges
intervene between the tracing ridge and the right delta, the tracing
is designated as an "outer"--O (fig. 281). All other tracings are
designated as "meeting"--M (figs. 282 to 287).

[Illustration: 282]

[Illustration: 283]

[Illustration: 284]

[Illustration: 285]

[Illustration: 286]

[Illustration: 287]

Tracing begins from the left delta. In no instance is a tracing to
begin on a type line. In figure 288, tracing begins at the short ridge
which is the left delta. It is true that inasmuch as the short ridge
ends immediately the type line is next followed, but this is only
because the type line is the next lower ridge. Its status as a type
line is independent