i. The earth (De terra) 1. The earth is placed in the central region of the world, standing fast in the center equidistant from all other parts of the sky. In the singular the word ‘earth’ (terra) signifies the whole globe, but in the plural, distinct parts. Logic supplies the earth's diverse names, for the word terra is derived from the upper surface that is worn away (terere); soil (humus) from the lower, or moist (humidus) earth, like that under the sea; ground (tellus), because we carry away (tollere) what it produces; as such it is also called Ops (i.e. the earth-goddess of plenty) because it produces wealth (ops) from its crops; and also ‘arable land’ (arvum), from plowing (arare) and cultivating. 2. However, to distinguish it properly from water, earth is called ‘dry land’ (aridum), as Scripture says (cf. Genesis 1:10): “God called the dry land (aridus) Earth.” The earth's natural attribute is that of dryness, for if it is moist, that comes from a union with water. Of its motion some say that it is the wind in its hollows that, itself moved, moves the earth. Sallust (Histories 2.28): “A number of mountains and hills subsided, sundered by the wind rushing through the hollows of the earth.” 3. Others maintain that life-giving water moves in the earth and simultaneously shakes it, like a vessel, as for instance Lucretius (see On the Nature of Things 6.555).