ing 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.

[Illustration: 142]

[Illustration: 143]

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.

[Illustration: 144]

[Illustration: 145]

[Illustration: 146]

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.

[Illustration: 147]

[Illustration: 148]

[Illustration: 149]

[Illustration: 150]

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 con