I was told by my grandfather that our Glass ancestors moved from the Highlands to North Northumberland probably late 17/early 18c. Was there some external event around then likely to motivate this move?
There was free movement within Britain and many Scots would have moved down to England to better their job prospects. You mention North Northumberland, and many Scots moved to Newcastle to become "keelmen", sailing the barges that took coal down the Tyne and out to ships which took it further afield -
"There is in Newcastle upon Tyne of keelmen, watermen, and other labourers, above 1800 able men, the most of them being Scottish men and Borderers which came out of the Tynedale and Reddesdale."
Harry