Vertically means that every class connected to the next class is connected to every class throughout the semester around a spiral.

纵向意味着每一节课都和下一节课有关系,和整个学期内的每一节课都有关系，呈一个螺旋状。

哈佛公开课 - 幸福课课程节选

Then what I'm going to do for the last twenty or twenty-five minutes is talk about the Dutch Republic.

接下来在这节课最后的二十到二十五分钟内,我会讲些关于荷兰共和国的知识

耶鲁公开课 - 欧洲文明课程节选