Hi Barry, when I spoke with you at Claymore you had asked about the long causeway, somewhere around the river Finn. Is was looking at a map of the area I don't know if you had noticed an area called Garrison hill and garrison lane, leading down to a bridge over the river Finn. It may a reference to some later garrison but it seems an odd place to put a garrison.
Was the references that mention the long causeway in relation to the campaign to take Derry or was it later.
I hope to make some enquiries tomorrow, will let you know if I have any luck
Billy