39. The continental divide refers to an imaginary line in the North American Rockies that divides the waters flowing into the Atlantic Ocean from those flowing into the Pacific. 大陆分水岭是指北美洛矶山脉上的一道想象线，该线把大西洋流域和太平洋流域区分开来。

　　40. Studies of the gravity field of the Earth indicate that its crust and mantle yield when unusual weight is placed on them. 对地球引力的研究表明，在不寻常的负荷之下地壳和地幔会发生位移。