The gradients on the Portpatrick Railway main line were severe: gently undulating from Castle Douglas to New Galloway, they then formed a stiff climb at 1 in 80 to Loch Skerrow, the alternately falling and rising at 1 in 76 to the summit at agethouse of Fleet. There was then an unbroken descent of 6½ miles (10½ km) at 1 in 80 to near Palnure. A less constant climb then led to a summit near the 40 milepost between Kirkcowan and Glenluce, then falling at a ruling gradient of 1 in 80 nearly to Challoch Junction. From Stranraer there was a stiff continuous climb at 1 in 72 to a summit at Colfin, at an elevation of 326 feet (99 m) above sea level, then a descent at 1 in 80 to Portpatrick.