Stalactite. When water holding lime in solution deposits it as it drops from the roof of a cavern, long rods of stone hang down like icicles, and these are called stalactites. Etym., σταλαζω, stalazo, to drop.
Stalagmite. When water holding lime in solution drops on the floor of a cavern, the water evaporating leaves a crust composed of layers of limestone: such a crust is called stalagmite, from σταλαγμα, stalagma, a drop, in opposition to stalactite, which see.
Statical Figure. The figure which results from the equilibrium of forces. From στατος, statos, stable, or standing still.
Sternum. The breast-bone, or the flat bone occupying the front of the chest.
Stilbite. A crystallized simple mineral, usually white, one of the Zeolite family, frequently included in the mass of the Trap-rocks.
Stratified. Rocks arranged in the form of strata, which see.
Stratification. An arrangement of rocks in strata, which see.
Strata, Stratum. The term stratum, derived from the Latin verb struo, to strew or lay out, means a bed or mass of matter spread out over a certain surface by the action of water, or in some cases by wind. The deposition of successive layers of sand and gravel in the bed of a river, or in a canal, affords a perfect illustration both of the form and origin of stratification. A large portion of the masses constituting the earth's crust are thus stratified, the successive strata of a given rock preserving a general parallelism to each other; but the planes of stratification not being perfectly parallel throughout a great extent like the planes of cleavage, which see.
Strike. The direction or line of bearing of strata, which is always at right angles to their prevailing dip.
Stufas. Jets of steam issuing from fissures in volcanic regions at a temperature often above the boiling point.