http://atlantic-cable.com//CableCos/CCC-Teleg/index.htm#mackay "Here's an 1886 report on the ship"
and from Alan
http://www.bbc.co.uk/iplayer/episode/p01n8f5d/clydebuilt-the-ships-that-made-the-commonwealth-2-the-cs-mackaybennett > Excellent programme available on iPlayer at the moment about a late 19th century cable ship and its role in recovering bodies from the Titanic disaster. Lots about the early history of subsea telegraphy and how they did it
complimentary articles on these issues by Stewart Ash are going to follow forthwith in several new posts. Also the updated report on the telegraphy seminar will be back soon