This work is partly carried out beneath the surface and partly on the surface, upon which the worms wander at night and eject the swallowed and triturated earth; frequently castings of some height are formed of coiled ropes of agglutinated particles of mould.
Very finely triturated soluble particles are rubbed into a smooth paste with an oil of the requisite consistency.
An amorphous form results when a mixture of iron filings and sulphur are triturated with water.