Slave labor quickly exhausted the soil and of its own force compelled the cutting of the forests and the extension of the area under cultivation.

奴隶劳动很快耗尽了土壤，并凭借自身的力量迫使砍伐森林和扩大耕种面积。

Ever active in their search for new fields as they exhausted the virgin soil of the older states, the restless subjects of King Cotton quickly reached the frontier of Louisiana.

当他们耗尽旧州的处女地时，他们一直积极寻找新的领域，科顿国王焦躁不安的臣民很快就到达了路易斯安那州的边境。