Stalactite and Stalagmite. Concretions of carbonate of lime and sometimes of other minerals, as quartz or even malachite, deposited by water dropping from the roof of a cavern or other vacant space.
Steatite. Soapstone.
Stigmaria. A coal fossil, an aquatic plant.
Stratification. The condition of rocks or accumulated minerals deposited in layers, beds, or strata.
Strike. The line of bearing of strata, or the direction of any horizontal line on a stratum.
Superposition. An expression very commonly employed by Geologists to describe the order of arrangement when one bed or stratum reposes upon another.
Supra-cretaceous. A term applied by Sir H. de la Bèche to rocks overlying the chalk. The term Tertiary is now universally adopted for this group.
Syenite. The granite of the quarries of Syene in Egypt. It is usual to call by this name any combination of quartz, feldspar, and hornblende.
Synclinal axis. The line of depression between two anticlinal axes.
Syncondrosis. Connection of bones by cartilage.