tinuation of ridge B.

[Illustration: 151]

[Illustration: 152]

[Illustration: 153]

[Illustration: 154]

[Illustration: 155]

[Illustration: 156]

Figures 157 and 158 are plain arches. Figure 158 cannot be said to be
a looping ridge, because by definition a loop must pass out or tend to
pass out upon the side from which it entered. This apparent loop
passes out upon the opposite side and cannot be said to tend to flow
out upon the same side.

[Illustration: 157]

[Illustration: 158]

In figures 159 and 160, there are ending ridges rising at about the
same degree from the horizontal plane.

Figure 159, however, is a plain arch, while 160 is a tented arch. This
differentiation is necessary because, if the first pattern were
printed crookedly upon the fingerprint card so that the ending ridge
was nearer the horizontal plane, there would be no way to ascertain
the true horizontal plane of the pattern (if the fissure of the finger
did not appear). In other words, there would be no means of knowing
that there was sufficient rise to be called an upthrust, so that it is
safe to classify the print as a plain arch only. In figure 160,
however, no matter how it is printed, the presence of a sufficient
rise could always be ascertained because of the space intervening
between the ending ridge and the ridge immediately beneath it, so that
it is safe to classify such a pattern as a tented arch. The test is,
_if the ridges on both sides of the ending ridge follow its direction
or flow trend, the print may be classified as a plain arch. If,
however, the ridges on only one side follow its direction, the print
is a tented arch_.

[Illustration: 159]

[Illustration: 160]

An upthrust, then, must not only be an ending ridge rising at a
sufficient degree from the horizontal plane, but there must also be a
space between the ending ridge and the ridge immediately beneath it.
_This, however, is not necessary for a short upthrust or spike, or any
upthrust which rises perpendicularly._

In connection with the proper classification to be assigned to those
borderline loop-tented arch cases where an appendage or spike is
thrusting out from the recurve, it is necessary to remember that _an
appendage or a spike abutting upon a recurve at right angles in the
space between the shoulders of a loop on the outside is considered to
spoil the recurve_.

If the appending ridge flows off the looping ridge smoothly in such a
way that