GLOSSARY. 
81 
the sense we use the term, but it is a chemical compound of 
sulphur and iron. 
Solfatara. A volcanic vent from which sulphur, sulphureous, 
watery, and acid vapours and gases are emitted. 
Sporules. The reproductory corpuscula (minute bodies) of cryp- 
togamic plains. Etym., airopa, spora, a seed. 
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., oraAafw, 
stalazo, to drop. 
Stalagmite. When water holding lime in solution drops on the 
floor of a cavern, the water evaporating leaves a crust com- 
posed of layers of limestone ; such a crust is called stalagmite, 
from (TTa\ayj.ia, stalagma, a drop, in opposition to stalactite, 
which see. 
Sti lbite. A white crystallized simple mineral, one of the Zeolite 
family, frequently included in the mass of the trap rocks. 
Stratified. Eocks arranged in the form of strata, which see. 
Stratification. An arrangement of rocks in strata, which see. 
Stratum, Strata. When several rocks lie like the leaves of a book, 
one upon another, each individual forms a stratum ; — strata is 
the plural of the word. Etym., stratum, part of a Latin verb 
signifying to strew or lay out. 
Strike. The direction or line of bearing of strata, which is always 
at right angles to their prevailing dip. For a fuller explana- 
tion, see vol. iii. p. 346. 
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. For geological acceptation of the term, see 
vol. iii. p. 358. 
Synclinal Axis. See explanation of this term, vol. iii. p. 293. 
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. 
Ta rsi. 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 
Vol. III. / 
