Bowl·der, Boul·der n.
 1. A large stone, worn smooth or rounded by the action of water; a large pebble.
 2. Geol. A mass of any rock, whether rounded or not, that has been transported by natural agencies from its native bed. See Drift.
 Bowlder clay, the unstratified clay deposit of the Glacial or Drift epoch, often containing large numbers of bowlders.
 Bowlder wall, a wall constructed of large stones or bowlders.
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 Clay n.
 1. A soft earth, which is plastic, or may be molded with the hands, consisting of hydrous silicate of aluminium. It is the result of the wearing down and decomposition, in part, of rocks containing aluminous minerals, as granite. Lime, magnesia, oxide of iron, and other ingredients, are often present as impurities.
 2. Poetry & Script. Earth in general, as representing the elementary particles of the human body; hence, the human body as formed from such particles.
    I also am formed out of the clay.   --Job xxxiii. 6.
 The earth is covered thick with other clay,
 Which her own clay shall cover.   --Byron.
 Bowlder clay. See under Bowlder.
 Brick clay, the common clay, containing some iron, and therefore turning red when burned.
 Clay cold, cold as clay or earth; lifeless; inanimate.
 Clay ironstone, an ore of iron consisting of the oxide or carbonate of iron mixed with clay or sand.
 Clay marl, a whitish, smooth, chalky clay.
 Clay mill, a mill for mixing and tempering clay; a pug mill.
 Clay pit, a pit where clay is dug.
 Clay slate Min., argillaceous schist; argillite.
 Fatty clays, clays having a greasy feel; they are chemical compounds of water, silica, and aluminia, as halloysite, bole, etc.
 Fire clay , a variety of clay, entirely free from lime, iron, or an alkali, and therefore infusible, and used for fire brick.
 Porcelain clay, a very pure variety, formed directly from the decomposition of feldspar, and often called kaolin.
 Potter's clay, a tolerably pure kind, free from iron.