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    Re: telegraphic longitude article
    From: Fred Hebard
    Date: 2003 Dec 26, 21:05 -0500

    I regret not having read Chauvenet's manual, which I expect covers all
    this (and hope I can understand the book when I receive it!).  But, how
    would this technique allow the transit times to be cancelled.  I
    apologize for my lack of comprehension.
    
    Fred Hebard
    
    On Dec 26, 2003, at 7:04 PM, George Huxtable wrote:
    
    > I doubt if there were relays involved in the telegraphs for that
    > purpose at
    > that time.  Observer A would tap a key when a star crossed (one of
    > many)
    > hairs in his transit telescope, and then a current pulse would flow
    > down
    > the wire. At both ends A and B of the wire would be a chronograph,
    > which
    > was a recording galvanometer, which drew a trace of the resulting
    > current-pulses. A single master-clock, somewhere in the system, added
    > timing pulses to the trace, at the two ends. Times were recorded at
    > both
    > ends when a star passed over observer A, and again when the same star
    > passed over observer B.
    >
    > This technique allowed the transit time of the elactrical signals to be
    > cancelled out.
    
    
    

       
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