Captain Ken #21 - Measuring the Depths

Captain Ken Owen had a long career at sea which included sailing as master with Overseas Containers Limited (OCL), P&O Containers and P&O Nedlloyd.   Ken is now retired and in 2020 he started writing a monthly article for publication using the pen name 'Captain Ken' in the Mellor Church Outlook magazine.

A number of articles that Ken has written are about his time at sea and he has very kindly agreed that we can share them here.  

In this, the 21st article in the series to be reproduced on the PONLHeritage site, Captain Owen goes back to his early days at sea when the depth of water was measured with a sounding line

This article was first published in the church magazine in February 2022.

During my time at sea, the art of navigation has completely changed.  The coming of GPS, of course is the main reason for this.  We now know exactly where we are without the skilled use of a sextant any more.  And as for the depth, we simply consult the chart, allowing only for tidal affect.  

It is already hard to remember that many ships did not have echo sounders, and still relied upon the sounding lead to measure the actual depth.  A special line with the depth indicated with distinctive marks, is bent on to the lead weight, which has a hollow in it’s bottom end, which when armed with white lead and tallow, collects a sample of the sea bed.  

The leadsman taking the soundings, would stand on a wooden platform protruding from the ship’s side, known as ‘the chains', and he would call out the depths he measured, by  shouting, ‘By the mark’ , if it was referring to one, or ‘By the deep’ if it was between actual marks.

It is interesting to know that Samuel Langhorne Clemens, the famous American author, made his pen name ‘Mark Twain’ which he had heard the leadsman call out, on a Mississippi steam boat.

I have very vivid memories from when as a teenage Midshipman, I was selected as leadsman as the ship approached  the  anchorage off Tacu Bar in the Yellow Sea in North China.  The sea was just turning to ice.  It was bitterly cold, and when I had called out  ‘By the mark ten’, my final sounding to the bridge, I realised that the line was frozen stiff down to the water.  My hands were just too cold to heave it up.  I have never felt more grateful than when an Able Bodied Seaman, passing on his way to the focsle, and wearing stout gloves, kindly pulled the line up for me, and coiled it neatly on the deck.  

Many ships both with and without echo sounders were equipped with a deep sea sounding machine.  This consisted of a winch, some electric and some manual, from which a wire fastened to a 26 pound lead was payed out directly in to the sea, and by resting a metal handle on the wire as it ran out, you could tell when it struck the bottom, and then start winding it in.


Attached to the lead was a glass tube filled with silver oxide which changed to red chloride when the sea water entered the tube.  The length of this when measured against a special gauge, indicated the depth.  This lead also collected a sample of the sea bottom.  

We were transiting the Taiwan Strait, in dense fog, and I so well remember having to carry this very heavy lead from the sounding machine on the poop, all the way to the bridge so the Captain could see for himself the bottom sample.  On one occasion, I dropped the lead on to the steel deck, while carrying it to the bridge, and the arming collected an amount of rust flakes.  However, the Captain was delighted when he saw it, as it resembled the shale that the chart told us was there.  

The voyage was successful, But I still feel a bit guilty for not explaining what had happened.

(This article was first published in the February 2022 edition of the Mellor Church Outlook Magazine).

For further articles in this series:

Captain Ken Owen's articles are being published on a regular basis here but if you are interested in reading others that he has written which we haven't yet used then please feel free to go to