They undulate like white sheets spread out in the sun, the clouds above the Lifford Bridge. They flow in the celestial vault, moved by the winds of the Atlantic, disregarding the border beneath them. The waters of the River Foyle seem to imitate them. There is no physical limit dividing those molecules. Borders are a human construct, just like that bridge: 115 meters of reinforced concrete connecting Lifford in Co Donegal, Republic of Ireland, with Strabane in Co Tyrone, Northern Ireland.