Part 5 (2/2)

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_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 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 or more.

- The type approaching the loop type, possessing two of the basic or essential characteristics of the loop, but lacking the third.

Figures 122 to 133 are examples of the tented arch.

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[Ill.u.s.tration: 123]

[Ill.u.s.tration: 124]

[Ill.u.s.tration: 125]

[Ill.u.s.tration: 126]

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[Ill.u.s.tration: 128]

[Ill.u.s.tration: 129]

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[Ill.u.s.tration: 132]

[Ill.u.s.tration: 133]

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 characteristic.

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