Turning those pages and studying their photographs is like flowing on a sad current that, like Blake's Thames, seems to "mark in every face, marks of weakness, marks of woe." (Para. 32)
Meaning: Moving those pages one by one and studying their photographs is something similar to moving on a sad current. The current, like the English poet William Blake's Thames, seems to leave marks of weakness and marks of great sadness in every human's face.
current: n. a continuous flowing movement of water, air, etc.
Be careful as this wire carries electrical current. 小心，这电线有电。
Strong water currents can be dangerous to swimmers. 急流对游泳者来说是危险的。
current: a. from or about the present time
Because of developments in international communication, current news is at hand almost everywhere. 由于国际通讯的发展，到处都可以收到时事新闻。
Current directions in military science place great importance on defense networks. 现代军事科学的趋势是注重防卫系统。