and so the tools of long ago have remained when even the bones of the men who made them have disappeared without trace.

因此，尽管制造这些工具的人的骨头早已荡然无存，但远古时代的石头工具却保存了下来。

for fear the agents of other firms should be able to trace the kind of research they are likely to be undertaking.

他们生怕别的公司的情报人员据此摸到他们可能要从事的某项科研项目。

but of accumulated knowledge applied to practical life.

而是积累起来的知识应用到实际生活中的结果。

Later, for its personal safety and practical needs,

慢慢地，由于自身安全和实际需要，

Parents would be greatly surprised and deeply touched if they realized how much belief their children usually have in their character and infallibility,

那么家长会大为吃惊和深受感动的，如果家长意识到孩子们通常是多么相信家长的品行和绝对正确，

From both maturity to death, a wave is subject to the same laws as any other'living'thing.

从成熟到消亡，波浪和其他任何活动中"的东西一样，都受制于共同的法则。