It is of great use to the sailor to know the length of his line, though he cannot with it fathom all the depths of the ocean.

It is of great use to the sailor to know the length of his line, though he cannot with it fathom all the depths of the ocean.

对水手来说，知道他的钓索的长度是很有用的，虽然他不能用它来测量海洋的全部深度。

-- John Locke 约翰·洛克