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    Re: Cable Repair
    From: Fred Hebard
    Date: 2003 Mar 26, 22:04 -0500

    I had been wondering why chronometer rates were being checked when
    accurate time was available over the cable.  One hypothesis was that
    the cable was broken, so accurate time was not avaiable.  To determine
    this, I examined the original cable-repair story
    (http://atlantic-cable.com/Article/Combe/).  In many cases, the sights
    were being taken when the cable was operating.  In the first case, the
    Cadiz-Teneriffe cable was broken, but they were taking time sights at
    the Cadiz
    
    
    
    
    
    
    
    
    
    
    
                                                               end, where
    accurate time should have been available from the Spanish land line.
    After repairing the Cadiz-Teneriffe line, they again took time sights
    in Cadiz.  In the second case, they checked their chronometers after
    finishing the repair of the Teneriffe-Cape Verde cable.  There also was
    a chronometer check in Teneriffe when the Cadiz-Teneriffe cable was
    still broken.
    
    It may be that time signals were not available at the proper time.
    After reading the wonderful link provided by Paul Hirose, it is clear
    that competent people were required to transmit telegraph time signals.
    For the cable repair vessels, there also were competent people on board
    ship to perform a direct check.  It is clear that the longitude of
    important places such as Cadiz and Teneriffe would have been
    established carefully at the time of this story.
    
    The wonderful link provided by Paul Hirose indicates that
    telegraph/cable time checks were encountering delays due to the speed
    of light over long distances.  But also suggests that transmission
    times were nearly instantaneous.  I guess relays close fast enough that
    the accumulated delay from them was insignificant.
    
    
    

       
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