it is now possible not only to locate a shoal but to tell if it is herring, cod, or other well-known fish, by the pattern of its echo.

不仅能够确定鱼群的位置，而且可以根据鱼群回声的特点分辨出是鲱鱼、鳕鱼，这是人们所熟悉的其他鱼。

The degree of secrecy naturally varies considerably.

保密程度自然差别很大。

Why does the idea of progress loom so large in the modern world? Surely progress of a particular kind is actually taking place around us and is becoming more and more manifest.

为什么进步这个概念在现代世界显得如此突出？无疑是因为有一种特殊的进步实际上正在我们周围发生，而且变得越来越明显。

As she was prepared for her maiden voyage on August 10, 1628, Stockholm was in a ferment.

在1628年8月10日，瓦萨号准备首航时，斯德哥尔摩一片欢腾。

But can we blame those who looked and failed to see what Galileo saw, if we remember that to use a telescope at the limit of its powers calls for long experience and intimate familiarity with one's instrument?

但是，如果我们想到，便用一架倍数有限的望远镜需要长期的经验和对自己仪器的熟悉程度，那么我们怎么能去责备观察了天空但没有看到伽利略所看到的东西的那些人呢？

gravity is the force that drives them in a continual attempt to restore the ocean surface to a flat plain.

地球引力是持续不断企图使海面复原为平面的力量。