Soil was being eroded and wasted along the Eastern seaboard, and they were using up the great soils of the Mississippi Valley and over time that slave system just somehow wasn't going to work out.

东部沿海地区的土地因被侵蚀而荒废掉,密西西比河谷地区的土地资源即将被耗尽,但就在这种情况下,奴隶制依然能维持南方的经济

耶鲁公开课 - 美国内战与重建课程节选

Others though, I want to tell you that it doesn't-- if you're shopping-- I had a student come by yesterday and ask he's a little rusty in his math skills if he should take this course.

其他的,我想告诉你们不必...,如果你还在挑选课程...,昨天有个学生来问我,他的数学有点荒废了,他该不该选这门课

耶鲁公开课 - 金融市场课程节选