The old man has, again, felt the need to apologise to his students.
And, of course, to himself.
If he didn't make assumptions, and rush blindly to be all-knowing, he would check his 'facts' (or at least, review the evidence).
He finds it difficult, in the middle of a navigation class, to consult reference books and websites; it rather spoils the flow of the presentation.
But he really should not have put-down the student who raised a perfectly valid question.
They were discussing height of tide, charted depth and depth of water. Someone asked how depth was measured in practice and he banged on for a bit about echo-sounders, sounding and then lead-lines.
Someone else asked whether the word 'sounding' pre-dated echo-sounders.
It flashed through the old man's mind that he was unsure, so he glossed over the question.
A glance at Falconer's 'Dictionary of the Marine' showed that, even in 1815, the word 'sound' had several meanings. His student was quite right: 'sounding the deep' had been used to mean measuring the depth of the sea since the 14th century, even though, at that time, they weren't sure what 'depth' or the 'deep' meant.
But surely they didn't use noises, or sound, as we do with echo-sounders, to measure the depth? They used lead-lines.
A glance at a dictionary of etymology solved the mystery: 'sound' has several meanings.
Yes, it means a noise, or making a noise.
But it also, in olden times, meant measuring the depth of the sea.
It became clear to the old man that he had done what many before him had done. He had confused two meanings of the word 'sound' and then conflated them.
An echo-sounder uses sound to sound the depth: a rather nice homographic pun: it would be nice to think that the inventor named it deliberately.
But, of course, every cloud has a silver lining.
The old man spent the whole of a rainy Saturday morning exploring his dictionaries and reference books.
