The Mahons were bound by a covenant to permit a coal company, which had sold to them or their predecessor only the surface rights to their lot, to remove all the coal without liability.

• 马洪受一项契约的限制，该契约规定只将地面部分的所有权卖给马洪及其继承人。 契约允许一个煤炭公司挖走地面以下的所有煤炭而不负任何责任。