048Europe in the High Middle Ages讲解

047Environmental Impact of the Anasazi讲解

046England’s Economy in the Sixteenth Century讲解

045Eli Terry’s Clock讲解

044Effects of the Commercial Revolution讲解

043Economic Decline in Europe During the Fourteenth Century讲解

042Earthquake Prediction讲解

041Earth’s Energy Cycle讲解

040Earth’s Atmosphere讲解

039Early Theories of Continental Drift讲解