Dominion Atlantic Railway
Bear River Bridge

Digby County, Nova Scotia





Dominion Atlantic Railway: Bear River Bridge, Digby County, Nova Scotia, 12 Nov 2010

Dominion Atlantic Railway    Bear River Bridge    12 November 2010

In November 2010 the bridge structure was still complete.
It appears here the same as it had for the last hundred years
(only the rails and the telegraph wires are missing).



Dominion Atlantic Railway: Bear River Bridge, Digby County, Nova Scotia, 12 Nov 2010

Dominion Atlantic Railway    Bear River Bridge    12 November 2010

The telegraph wires are something of a puzzle.  The wires were removed years ago,
but there is  plainly  visible  evidence – here  shown  circled – that they  once  existed.
These wooden arms, manufactured (complete with transposition brackets and threaded
wood  pins for  glass  insulators)  to serve as  crossarms  on telegraph  poles  but here
installed as  cantilevered  extensions  of railway ties, were used by the railway to carry
its telegraph  wires  across this river.  For many  decades  the electric  telegraph was a
vital communication  system,  essential  to the safe  and efficient  operation of  trains on
this single-track main line.  The telegraph required a continuous electric circuit connecting
each station along the  entire  length  of the  railway.  On dry land  the wires were usually
carried on  poles  beside the railway, but  poles  could  not  be used to cross wide rivers.
To get the  wires  across this river, the railway  installed the  wooden arms  shown here.
These worked  very  well along  trusses  which were  permanently  in place, but what
about the  swing  span?  The swing  span  is a  puzzle.  The  telegraph  wires  would
interfere with the  sideways  movement  of the span.  How were the  telegraph  wires
placed adjacent to the swing span?  Remember, the telegraph required a continuous
electric  circuit;  no  gaps  could  exist  anywhere.  What  to  do?  It  was  impractical
to provide arms  long  enough to reach out  horizontally  far enough stay clear of the
swing span  at all  positions.  Even if  this could  be done with  very  long  arms there
was the problem of tall masts on ships as they passed.  It wasn't  enough  to move the
wires  horizontally,  they also  had to be  placed  vertically  high  enough  to be sure that
they would not be  snagged  by any part of  any ship  that might happen  to pass this way.
My guess is that the telegraph circuit was taken across rivers, where a swing span existed,
by an  underwater  cable.  Reliable  underwater  cables,  suitable for an  electric telegraph
circuit, had been  developed  in the  1850s and 1860s, years  before  this railway  was built.
My guess is that the  telegraph  wires  were carried across by extension arms on the bridge
only  after  it was  officially  recognized  that the  swing  spans  in the  railway  bridges  had
outlived their usefulness and the appropriate authorities agreed that they would no longer
be required.  From the railway's point of view, the main  advantage  would be that swing
span operators would  no longer  be required.  The underwater telegraph cables could
remain in place  as long as  they continued to work, but  any  time  a cable developed
a problem  it would not  be repaired  but would be  replaced  by the  extension  arms
installed on the bridge.  That's my guess.  No doubt there are people who know how
railway telegraph wires were installed at locations where bridges had swing spans.



Dominion Atlantic Railway: Bear River Bridge, Digby County, Nova Scotia, 12 Nov 2010

Dominion Atlantic Railway    Bear River Bridge    12 November 2010

This is another view showing the telegraph arms along the side of the bridge.





Go To:   Photographs of the Bear River bridge
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    http://ns1758.ca/rail/dar-bridge-sissiboo.html

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First uploaded to the WWW:   2011 December 10