Articles from The Science Of Fingerprints
Radial And Ulnar Loops
Establishment Of A Local Fingerprint Identification Bureau
The Identification Division Of The Fbi
The Tented Arch
In the tented arch, most of the ridges enter upon one side of the
impression and flow or tend to flow out upon the other side, as in the
plain arch type; however, the ridge or ridges at the center do not.
There are three types of tented arches:
- The type in which ridges at the center form a definite
angle; i.e., 90 deg. or less.
- The type in which one or more ridges at the center form an
upthrust. An upthrust is an ending ridge of any length
rising at a sufficient degree from the horizontal plane;
i.e., 45 deg. or more.
- The type approaching the loop type, possessing two of the
basic or essential characteristics of the loop, but lacking
Figures 122 to 133 are examples of the tented arch.
Figures 122 to 124 are of the type possessing an angle.
Figures 125 to 129 reflect the type possessing an upthrust.
Figures 130 to 133 show the type approaching the loop but lacking one
Tented arches and some forms of the loop are often confused. It should
be remembered by the reader that the mere converging of two ridges
does not form a recurve, without which there can be no loop. On the
other hand, there are many patterns which at first sight resemble
tented arches but which on close inspection are found to be loops, as
where one looping ridge will be found in an almost vertical position
within the pattern area, entirely free from and passing in front of
Figure 134 is a tented arch. The ridge marked A--A in the sketch
enters on one side of the impression and flows to the other with an
acute rise in the center. Ridge C strikes into A at point B and should
not be considered as a bifurcating ridge. The ridges marked D--D
would form a tented arch if the rest of the pattern were absent.
Figure 135 is a sketch of a pattern reflecting a ridge, A--B, entering
on one side of the impression, recurving, and making its exit on the
other side of the impression. The reader should study this sketch
carefully. It should be borne in mind that there must be a ridge
entering on one side of the impression and recurving in order to make
its exit on the same side from which it entered, or having a tendency
to make its exit on that side, before a pattern can be considered for
possible classification as a loop. This pattern is a tented arch of
the upthrust type. The upthrust is C. There is also an angle at E. D
cannot be termed as a delta, as the ridge to the left of D cannot be
considered a type line because it does not diverge from the ridge to
the right of D but turns and goes in the same direction.
In connection with the types of tented arches, the reader is referred
to the third type. This form of tented arch, the one which approaches
the loop, may have any combination of two of the three basic loop
characteristics, lacking the third. These three loop characteristics
are, to repeat:
- A sufficient recurve.
- A delta.
- A ridge count across a looping ridge.
It must be remembered that a recurve must be free of any appendage
abutting upon it at a right angle between the shoulders, and a true
ridge count is obtained only by crossing a looping ridge freely, with
a white space intervening between the delta and the ridge to be
Figures 136 and 137 are tented arches having loop formations within
the pattern area but with deltas upon the loops, by reason of which it
is impossible to secure a ridge count. The type lines run parallel
from the left in figures 136 and 137. These tented arches have two of
the loop characteristics, recurve and delta, but lack the third, the
In figure 138, the reader will note the similarity to the figures 136
and 137. The only difference is that in this figure the type lines are
running parallel from the right. It will be noted from these three
patterns that the spaces between the type lines at their divergence
show nothing which could be considered as delta formations except the
looping ridges. Such patterns are classified as tented arches because
the ridge count necessary for a loop is lacking.
Figure 139 is an example of a tented arch. In this pattern, if the
looping ridge approached the vertical it could possibly be a one-count
loop. Once studied, however, the pattern presents no real difficulty.
There are no ridges intervening between the delta, which is formed by
a bifurcation, and the core. It will be noted that the core, in this
case, is at the center of the recurve, unlike those loops which are
broadside to the delta and in which the core is placed upon the
shoulder. This pattern has a recurve and a separate delta, but it
still lacks the ridge count necessary to make it a loop.
Figures 140 and 141 are examples of tented arches. These two figures
are similar in many ways. Each of these prints has three abrupt ending
ridges but lacks a recurve; however, in figure 141 a delta is present
in addition to the three abrupt ending ridges. This condition does not
exist in figure 140, where the lower ending ridge is the delta.
When interpreting a pattern consisting of two ending ridges and a
delta but lacking a recurve, do not confuse the ridge count of the
tented arch with that of the ridge count for the loop. The ridge count
of the tented arch is merely a convention of fingerprinting, a fiction
designed to facilitate a scientific classification of tented arches,
and has no connection with a loop. To obtain a true ridge count there
must be a looping ridge which is crossed freely by an imaginary line
drawn between the delta and the core. The ridge count referred to as
such in connection with the tented arches possessing ending ridges and
no recurve is obtained by imagining that the ending ridges are joined
by a recurve only for the purpose of locating the core and obtaining a
ridge count. If this point is secure in the mind of the classifier,
little difficulty will be encountered.
Figures 140 and 141, then, are tented arches because they have two of
the characteristics of a loop, delta and ridge count, but lack the
third, the recurve.
Figure 142 is a loop formation connected with the delta but having no
ridge count across a looping ridge. By drawing an imaginary line from
the core, which is at the top of the rod in the center of the pattern,
to the delta, it will be noted that there is no recurving ridge
passing between this rod and the delta; and, therefore, no ridge count
can result. This pattern is classified as a tented arch. There must be
a white space between the delta and the first ridge counted, or it may
not be counted. Figure 143 is also a tented arch because no ridge
count across a looping ridge can be obtained, the bifurcations being
connected to each other and to the loop in a straight line between
delta and core. The looping ridge is not crossed freely. No white
space intervenes between the delta and the loop. These patterns are
tented arches because they possess two of the characteristics of a
loop, a delta and a recurve, but lack the third, a ridge count across
a looping ridge.
Figure 144 is a tented arch combining two of the types. There is an
angle formed by ridge a abutting upon ridge b. There are also the
elements of the type approaching a loop, as it has a delta and ridge
count but lacks a recurve.
Figures 145 to 148 are tented arches because of the angles formed by
the abutting ridges at the center of the patterns.
Figure 149 is a tented arch because of the upthrust present at the
center of the pattern. The presence of the slightest upthrust at the
center of the impression is enough to make a pattern a tented arch.
An upthrust must be an ending ridge. If continuous as in figure 150,
no angle being present, the pattern is classified as a plain arch.
Figures 151 to 153 are plain arches. Figure 154 is a tented arch.
Figure 155 is a plain arch because it is readily seen that the
apparent upthrust A is a continuation of the curving ridge B. Figure
156 is a tented arch because ridge A is an independent upthrust, and
not a continuation of ridge B.
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.
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.
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 it forms a bifurcation and not an abutment of two ridges at a
right angle, the recurve is considered as remaining intact. The test
is to trace the looping ridge toward the appendage, and if, when it is
reached, the tracing may be continued as readily upon the appendage as
upon the looping ridge, with no sudden, sharp change of direction, the
recurve is sufficient. Figures 161 to 184 should be studied with this
[Illustration: 161. Tented arch.]
[Illustration: 162. Tented arch.]
[Illustration: 163. Tented arch.]
[Illustration: 164. Tented arch.]
[Illustration: 165. Tented arch.]
[Illustration: 166. Tented arch.]
[Illustration: 167. Tented arch.]
[Illustration: 168. Tented arch.]
[Illustration: 169. Loop.]
[Illustration: 170. Loop.]
[Illustration: 171. Loop.]
[Illustration: 172. Loop.]
[Illustration: 173. Loop.]
[Illustration: 174. Loop.]
[Illustration: 175. Loop.]
[Illustration: 176. Tented arch.]
[Illustration: 177. Tented arch.]
[Illustration: 178. Tented arch.]
[Illustration: 179. Loop.]
[Illustration: 180. Loop.]
[Illustration: 181. Loop.]
[Illustration: 182. Loop.]
[Illustration: 183. Loop.]
[Illustration: 184. Loop.]
Figures 185 to 190 show additional examples of tented arches.
The reason that figure 185 is given the classification of a tented
arch is because of the presence of all the loop requirements with the
exception of one, which is the recurve. In this pattern appear three
ending ridges. The lowest ending ridge provides the delta, and the
other two by the convention explained previously, provide the ridge
count. It is a tented arch, then, of the type approaching the loop,
with two of the characteristics, but lacking the third, a recurve.
Figures 186 and 187 are tented arches of the same type. A close
examination of these prints will reveal that when the imaginary line
is drawn between delta and core no ridge count across a looping ridge
can be obtained. It must be remembered that the core of a loop may not
be placed below the shoulder line. Lacking one of the three
characteristics of a loop, these patterns must be classified as tented
arches. When figure 188 is examined, it will be noticed that the
recurve is spoiled by the appendage abutting upon it between the
shoulders at a right angle, so it must also be classified with the
tented arches. In figure 189, the only possible delta must be placed
upon the looping ridge, thus preventing a ridge count although delta
and recurve are present. Figure 190 is assigned the classification of
a tented arch. One of the requirements of a loop type is that the
ridge enters on one side, recurves, and makes its exit on the side
from which it entered. This, of course, makes it necessary that the
ridge pass between the delta and the core. It will be noted from this
figure that although this ridge passes between the delta and the core,
it does not show any tendency to make its exit on the side from which
it entered, and therefore the loop classification is precluded, and it
is a tented arch.
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