Some of the Author's friends, who had read the first and second volumes or the Principles of Geology, having met with difficulties from their previous unacquaintance with the technical terms used in Geology and Natural History, suggested to him that a Glossary of those words would render his work much more accessible to general readers. The Author willingly complied with this suggestion, but finding that his own familiarity with the subject made him not a very competent judge of the terms that required explanation, he applied to the friends above alluded to for their assistance, and from lists of words supplied by them, the following Glossary has been constructed. It will be obvious to men of science, that in order to attain the object in view, it was necessary to employ illustrations and language as familiar as possible to the general reader.
Acephalous. The Acephala are that division of molluscous animals which, like the oyster and scallop, are without heads. The class Acephala of Cuvier comprehends many genera of bivalve shells, and a few genera of mollusca which are devoid of shells. Etym., a, without, and, cephale, the head.
Algae. An order or division of the cryptogamic class of plants, The whole of the sea-weeds are comprehended under this division, and the application of the term in this work is to marine plants. Etym., Alga, sea-weed.
Alum-stone, Alumen, Aluminous. Alum is the base of pure clay, and strata of clay are often met with containing much iron-pyrites. When the latter substance decomposes, sulphuric acid is produced, which unites with the aluminous earth of the clay to form sulphate of alumine, or common alum. Where manufactories are established for obtaining the alum, the indurated beds_ of clay employed are called Alum-stone.
Alluvial. The adjective of alluvium, which see.
Alluvion. Synonymous with alluvium, which see.
Aluvium. Earth, sand, gravel, stones, and other transported matter which has been washed away and thrown down by rivers, floods, or other causes, upon land not permanently submerged beneath the waters of lakes or seas. Etym., Alluo, to wash upon. For a further explanation of the term, as used in this work, see vol. ii. chap. xiv., and vol. iii. p. 145.
Ammonite. An extinct and very numerous genus of the order of molluscous animals, called Cephalopoda, allied to the modern genus Nautilus, which inhabited a chambered shell, curved like a coiled snake. Species of it are found in all geological periods of the secondary strata; but they have not yet been seen in the tertiary beds. They are named from their resemblance to the horns on the statues of Jupiter Ammon.
Amorphous. Bodies devoid of regular form. Etym.,a, without, and, morphe, form.
Amygdaloid. One of the forms of the Trap-rocks, in which agates and simple minerals appear to be scattered like almonds in a cake. Etym.,amygdala, an almond.
Analcime. A simple mineral of the Zeolite family, of frequent occurrence in the trap-rocks.
Analogue. A body that resembles or corresponds with another body. A recent shell of the same species as a fossil-shell, is the analogue of the latter.
Anoplothere, Anoplotherium. A fossil extinct quadruped belonging to the order Pachydermata, resembling a pig. It has received its name because the animal must have been singularly wanting in means of defence, from the form of its teeth and the absence of claws, hoofs, and horns. Etym., anoplos, unarmed, and therion, a wild beast.
Antagonist Powers. Two powers in nature, the action of the one counteracting that of the other, by which a kind of equilibrium or balance is maintained, and the destructive effect prevented that would be produced by one operating without a check.
Antenne. The articulated horns with which the heads of insects are invariably furnished.
Anthracite. A shining substance like black-lead ; a species of mineral charcoal. Etym.,anthrax,coal.
Anthracotherium. A name given to an extinct quadruped, supposed to belong to the Pachydermata, the bones of which were found in lignite and coal of thertiary strata. Etym.,anthrax, coal, and therion, wild beast.
Anthropomorphous. Having a form resembling the human. Etym., anthropos, a man, morphe, form,
Anticlinal Axis. If a range of hills, or a valley, be composed of strata, which on the two sides dip in opposite directions, the imaginary line that lies between them, towards which the strata on each side rise, is called the anticlinal axis. In a row of houses with steep roofs facing the south, the slates represent inclined strata dipping north and south, and the ridge is an east and west anticlinal axis. For a farther explanation, with a diagram, see vol, iii. p. 293.
AntisepticEtymantsepo