Subapennines. Low hills which skirt or lie at the foot of the great chain of the Apennines in Italy. The term. Subapennine is applied geologically to a series of strata of the Older Pliocene Period.
Syenite. A kind of granite; so called, because it was brought from Syene in Egypt.
Talus. When fragments are broken off by the action of the weather from the face of a steep rock, as they accumulate at its foot, they form a sloping heap, called a talus. The term is borrowed from the language of fortification, where talus means the outside of a wall of which the thickness is diminished by degrees, as it rises in height, to make it the firmer.
Tarsi. The feet in insects, which are articulated, and formed of five or a less number of joints.
Tertiary Strata. A series of sedimentary rocks, with characters which distinguish them from two other great series of strata—the secondary and primary—which lie beneath them.
Testacea. Molluscous animals, having a shelly covering. Etym., testa, a shell, such as snails, whelks, oysters, &c.
Thallogens. A class of flowerless plants including all those that have no defined axis, stem, or leaves; as Lichens, Seaweeds, and Fungi. Etym., θαλλος, thallos, a branch, and γενεσις, genesis, increase.
Thermal. Hot. Etym., θερμος, thermos, hot.
Thermo-electricity. Electricity developed by heat.
Thin Out. When a stratum, in the course of its prolongation in any direction, becomes gradually less in thickness, the two surfaces approach nearer and nearer; and when at last they meet, the stratum is said to thin out or disappear.