the exact location is 55"36'15.57 North 2"44'36.36 West or thereabouts
It was a bit East from the above coordinates, apparently (Google Maps direct link, Multimap direct link). Here is a page on the Berwickshire Railway. I note that the line from which it branched off just before the viaduct, the Edinburgh and Hawick Railway, is to be raised from the dead as the Waverley Railway. *Traitor*, n. A benighted individual who perceives an illusory distinction between serving his nation and abetting the criminals who govern it.