[Fig. 134]
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.
[Fig. 135]
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.