Loam, an earthy rock composed of clay and sand neither of which amounts to 75 per cent. of the whole. It is commonly yellow, brown, or red from iron oxide, and occurs most frequently as the result of river-floods over alluvial meadows. From one of its chief uses it is known as brick-earth. When sandy - i.e. containing 60 to 70 per cent. of sand - it is added to stiff clays to lighten them, a process erroneously termed "marling," and thus some loams, such as those of the Upper Trias or Keuper, have been misnamed Marl (q.v.). Whether natural or artificial, most ordinary garden soil is a loam with a greater or less admixture of vegetable matter or humus (q.v.).